You searched for +publisher:"Virginia Tech" +contributor:("Loos, Alfred C.").
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Virginia Tech
1.
Furrow, Keith W.
Environmental effects on stitched RTM composites.
Degree: MS, Engineering Mechanics, 1993, Virginia Tech
URL: http://hdl.handle.net/10919/44770 
► The effects of temperature and humidity cycling on mechanical properties of AS4/3501-6 quasi-isotropic composites prepared from unstitched, Kevlar 29 stitched, and S-2 glass stitched…
(more)
▼
The effects of temperature and humidity cycling on mechanical properties of
AS4/3501-6 quasi-isotropic composites prepared from unstitched, Kevlar 29
stitched, and S-2 glass stitched uniweave fabric were determined. Data presented
include compression strengths and compression-compression fatigue results for
environmentally cycled and uncycled composites. Ten1perature cycling ranged
from 60°
C to -55°
C. The relative humidity varied between 95 percent at the high
temperature and a percent at the low temperature. Microcracks which were found
predominantly around individual stitches were recorded using photomicrographs
taken at the end of each cycling period. The glass stitched and Kevlar stitched
laminates showed significant microcracking before cycling. The unstitched
uniweave material developed microcracks only after cycling. The glass stitched
material had lower baseline compression strength than the unstitched and Kevlar
stitched materials. Temperature and humidity cycling reduced the static
compression strength of the unstitched and Kevlar stitched uniweave materials
nearly 10 percent. Under the same conditions the glass stitched uniweave
material lost 3 percent of its baseline strength. Combined temperature and
humidity cycling did not effect the fatigue properties of the uniweave materials
when the test specimens were dried to their original weights before testing.
Advisors/Committee Members: Loos, Alfred C. (committeechair), Hyer, Michael W. (committee member), Dillard, David A. (committee member).
Subjects/Keywords: Fibrous composites; LD5655.V855 1993.F877
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APA (6th Edition):
Furrow, K. W. (1993). Environmental effects on stitched RTM composites. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/44770
Chicago Manual of Style (16th Edition):
Furrow, Keith W. “Environmental effects on stitched RTM composites.” 1993. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/44770.
MLA Handbook (7th Edition):
Furrow, Keith W. “Environmental effects on stitched RTM composites.” 1993. Web. 17 Apr 2021.
Vancouver:
Furrow KW. Environmental effects on stitched RTM composites. [Internet] [Masters thesis]. Virginia Tech; 1993. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/44770.
Council of Science Editors:
Furrow KW. Environmental effects on stitched RTM composites. [Masters Thesis]. Virginia Tech; 1993. Available from: http://hdl.handle.net/10919/44770
Virginia Tech
2.
Davis, Kedzie.
The effect of cooling rate on toughness and crystallinity in poly(ether ketone ketone) (PEKK)/G30-500 composites.
Degree: MS, Materials Science and Engineering, 1996, Virginia Tech
URL: http://hdl.handle.net/10919/44807
Subjects/Keywords: mode I and mode II strain energy release rates; interlaminar fracture toughness; carbon fiber composites; PEKK; degree of crystallinity; LD5655.V855 1996.D3835
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APA (6th Edition):
Davis, K. (1996). The effect of cooling rate on toughness and crystallinity in poly(ether ketone ketone) (PEKK)/G30-500 composites. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/44807
Chicago Manual of Style (16th Edition):
Davis, Kedzie. “The effect of cooling rate on toughness and crystallinity in poly(ether ketone ketone) (PEKK)/G30-500 composites.” 1996. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/44807.
MLA Handbook (7th Edition):
Davis, Kedzie. “The effect of cooling rate on toughness and crystallinity in poly(ether ketone ketone) (PEKK)/G30-500 composites.” 1996. Web. 17 Apr 2021.
Vancouver:
Davis K. The effect of cooling rate on toughness and crystallinity in poly(ether ketone ketone) (PEKK)/G30-500 composites. [Internet] [Masters thesis]. Virginia Tech; 1996. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/44807.
Council of Science Editors:
Davis K. The effect of cooling rate on toughness and crystallinity in poly(ether ketone ketone) (PEKK)/G30-500 composites. [Masters Thesis]. Virginia Tech; 1996. Available from: http://hdl.handle.net/10919/44807
Virginia Tech
3.
Kon, Haruhiko.
Characterization of adhesively bonded joints using bulk adhesive properties.
Degree: MS, Engineering Mechanics, 1991, Virginia Tech
URL: http://hdl.handle.net/10919/40756
► Though using bulk adhesive properties to predict adhesively bonded joint response has yet to be proven infallible, based upon the success of previous works,…
(more)
▼ Though using bulk adhesive properties to predict adhesively
bonded joint response has yet to be proven infallible, based upon the
success of previous works, this effort attempts to shed some light on
the stresses present in a typical automotive bonded joint. Adhesive
material properties obtained in previous works were used in a finite
element analysis of a simulated automotive joint to predict the
stresses in that joint.
The automotive joint analyzed was a simplified representation
of a joint provided by General Motors. The specifications included
the rate or stiffness of the joint and the materials to be used. The
basic design of the joint is a rectangular solid section steel frame to
which an SMC panel is bonded using Ashland Chemical urethane
based adhesives.
Due to computer time constraints and problem complexity, a
complete analysis including a time dependent, viscoelastic analysis
was not possible. The linear elastic case analyzed gave important
insight into the magnitudes of stresses to be expected in a typical
joint. It was found that for an applied load to produce a 1 degree
deflection in the steel frame, the stresses in the adhesive were below
20% of the ultimate tensile strength of the adhesive. This low stress
state is significant because the adhesive behaves as a linear viscoelastic material in that range, making further analysis less
complicated and time consuming.
Advisors/Committee Members: Grant, John Wallace (committeechair), Griffin, Odis Hayden Jr. (committee member), Loos, Alfred C. (committee member).
Subjects/Keywords: Joints (Engineering); LD5655.V855 1991.K66
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APA (6th Edition):
Kon, H. (1991). Characterization of adhesively bonded joints using bulk adhesive properties. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/40756
Chicago Manual of Style (16th Edition):
Kon, Haruhiko. “Characterization of adhesively bonded joints using bulk adhesive properties.” 1991. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/40756.
MLA Handbook (7th Edition):
Kon, Haruhiko. “Characterization of adhesively bonded joints using bulk adhesive properties.” 1991. Web. 17 Apr 2021.
Vancouver:
Kon H. Characterization of adhesively bonded joints using bulk adhesive properties. [Internet] [Masters thesis]. Virginia Tech; 1991. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/40756.
Council of Science Editors:
Kon H. Characterization of adhesively bonded joints using bulk adhesive properties. [Masters Thesis]. Virginia Tech; 1991. Available from: http://hdl.handle.net/10919/40756
Virginia Tech
4.
McGrane, Rebecca Ann.
Vacuum Assisted Resin Transfer Molding of Foam Sandwich Composite Materials: Process Development and Model Verification.
Degree: MS, Engineering Science and Mechanics, 2001, Virginia Tech
URL: http://hdl.handle.net/10919/42108
► Vacuum assisted resin transfer molding (VARTM) is a low cost resin infusion process being developed for the manufacture of composite structures. VARTM is being evaluated…
(more)
▼ Vacuum assisted resin transfer molding (VARTM) is a low cost resin infusion process being developed for the manufacture of composite structures. VARTM is being evaluated for the manufacture of primary aircraft structures, including foam sandwich composite materials. One of the benefits of VARTM is the ability to resin infiltrate large or complex shaped components. However, trial and error process development of these types of composite structures can prove costly and ineffective. Therefore, process modeling of the associated flow details and infiltration times can aide in manufacturing design and optimization.
The purpose of this research was to develop a process using VARTM to resin infiltrate stitched and unstitched dry carbon fiber preforms with polymethacrylimide foam cores to produce composite sandwich structures. The infiltration process was then used to experimentally verify a three-dimensional finite element model for VARTM injection of stitched sandwich structures.
Using the processes developed for the resin infiltration of stitched foam core preforms, visualization experiments were performed to verify the finite element model. The flow front progression as a function of time and the total infiltration time were recorded and compared with model predictions. Four preform configurations were examined in which foam thickness and stitch row spacing were varied. For the preform with 12.7 mm thick foam core and 12.7 mm stitch row spacing, model prediction and experimental data agreed within 5%. The 12.7 mm thick foam core preform with 6.35 mm row spacing
experimental and model predicted data agreed within 8%. However, for the 12.7 mm thick foam core preform with 25.4 mm row spacing, the model overpredicted infiltration times by more 20%. The final case was the 25.4 mm thick foam core preform with 12.7 mm row spacing. In this case, the model overpredicted infiltration times by more than 50%. This indicates that the model did not accurately describe flow through the needle perforations in the foam core and could be addressed by changing the mesh elements connecting the two face sheets.
Advisors/Committee Members: Loos, Alfred C. (committeechair), Batra, Romesh C. (committee member), Gürdal, Zafer (committee member).
Subjects/Keywords: vacuum assisted resin transfer molding; polymer composite processing; sandwich structures; VARTM
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APA (6th Edition):
McGrane, R. A. (2001). Vacuum Assisted Resin Transfer Molding of Foam Sandwich Composite Materials: Process Development and Model Verification. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/42108
Chicago Manual of Style (16th Edition):
McGrane, Rebecca Ann. “Vacuum Assisted Resin Transfer Molding of Foam Sandwich Composite Materials: Process Development and Model Verification.” 2001. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/42108.
MLA Handbook (7th Edition):
McGrane, Rebecca Ann. “Vacuum Assisted Resin Transfer Molding of Foam Sandwich Composite Materials: Process Development and Model Verification.” 2001. Web. 17 Apr 2021.
Vancouver:
McGrane RA. Vacuum Assisted Resin Transfer Molding of Foam Sandwich Composite Materials: Process Development and Model Verification. [Internet] [Masters thesis]. Virginia Tech; 2001. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/42108.
Council of Science Editors:
McGrane RA. Vacuum Assisted Resin Transfer Molding of Foam Sandwich Composite Materials: Process Development and Model Verification. [Masters Thesis]. Virginia Tech; 2001. Available from: http://hdl.handle.net/10919/42108
Virginia Tech
5.
Hammond, Vincent H.
Verification of a two-dimensional infiltration model for the resin transfer molding process.
Degree: MS, Engineering Mechanics, 1993, Virginia Tech
URL: http://hdl.handle.net/10919/41537
► A two-dimensional fmite element model for the infiltration of a dry textile preform by an injected resin has been verified. The model, which is based…
(more)
▼ A two-dimensional fmite element model for the infiltration of a dry textile preform
by an injected resin has been verified. The model, which is based on the finite
element/control volume technique, determines the total infiltration time and the
pressure increase at the mold inlet associated with the RTM process. Important input
data for the model are the compaction and permeability behavior of the preform
along with the kinetic and rheological behavior of the resin.
The compaction behavior for several textile preforms was determined by
experimental methods. A power law regression model was used to relate fiber
volume fraction to the applied compaction pressure. Results showed a large increase
in fiber volume fraction with the initial application of pressure. However, as the
maximum fiber volume fraction was approached, the amount of compaction pressure
required to decrease the porosity of the preform rapidly increased.
Similarly, a power law regression model was used to relate permeability to the fiber
volume fraction of the preform. Two methods were used to measure the permeability
of the textile preform. The first, known as the steady state method, measures the
permeability of a saturated preform under constant flow rate conditions. The second,
denoted the advancing front method, determines the permeability of a dry preform
to an infiltrating fluid. Water, corn oil, and an epoxy resin, Epon 815, were used to
determine the effect of fluid type and viscosity on the steady state permeability
behavior of the preform. Permeability values measured with the different fluids
showed that fluid viscosity had no influence on the permeability behavior of 162 E-glass and TTI IM7/8HS preforms.
Permeabilities measured from steady state and advancing front experiments for the
warp direction of 162 E-glass fabric were similar. This behavior was noticed for tests
conducted with corn oil and Epon 815. Comparable behavior was observed for the
warp direction of the TTl 1M7/8HS preform and corn oil.
Fluid/fiber interaction was measured through the use of the single fiber pull-out test.
The surface tension of both the corn oil and Epon 815 was determined. The contact
angle between these two fluids and glass and carbon fibers was also measured. These
tests indicated that the glass fiber had a lower contact angle than the carbon fiber
and therefore is wet out better than the carbon fiber by both fluids. This result is
attributed to the sizing commonly used on the carbon fibers.
Mold filling and flow visualization experiments were performed to verify the
analytical computer model. Frequency dependent electromagnetic sensors were used
to monitor the resin flow front as a function of time. For the flow visualization tests,
a video camera and high resolution tape recorder were used to record the
experimental flow fronts. Comparisons between experimental and model predicted
flow fronts agreed well for all tests. For the mold filling tests conducted at constant
flow rate injection, the model was able to accurately predict the…
Advisors/Committee Members: Loos, Alfred C. (committeechair), Grant, J. Walter (committee member), Kuppusamy, Thangavelu (committee member).
Subjects/Keywords: Industrial fabrics; LD5655.V855 1993.H3636
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APA (6th Edition):
Hammond, V. H. (1993). Verification of a two-dimensional infiltration model for the resin transfer molding process. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/41537
Chicago Manual of Style (16th Edition):
Hammond, Vincent H. “Verification of a two-dimensional infiltration model for the resin transfer molding process.” 1993. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/41537.
MLA Handbook (7th Edition):
Hammond, Vincent H. “Verification of a two-dimensional infiltration model for the resin transfer molding process.” 1993. Web. 17 Apr 2021.
Vancouver:
Hammond VH. Verification of a two-dimensional infiltration model for the resin transfer molding process. [Internet] [Masters thesis]. Virginia Tech; 1993. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/41537.
Council of Science Editors:
Hammond VH. Verification of a two-dimensional infiltration model for the resin transfer molding process. [Masters Thesis]. Virginia Tech; 1993. Available from: http://hdl.handle.net/10919/41537
Virginia Tech
6.
MacRae, John Douglas.
Development and verification of a resin film infusion/resin transfer molding simulation model for fabrication of advanced textile composites.
Degree: MS, Engineering Mechanics, 1994, Virginia Tech
URL: http://hdl.handle.net/10919/42574
► The objective of this study was to develop a two-dimensional computer model for the simulation of the resin transfer molding/resin film infusion processing of…
(more)
▼ The objective of this study was to develop a two-dimensional computer model for the simulation
of the resin transfer molding/resin film infusion processing of advanced composite
materials. This computer simulation model is designed to provide aircraft structure and
tool designers with a method of predicting the infiltration and curing behavior of a composite
material component. For a given specified cure cycle, the computer model can be
used to calculate the resin infiltration, resin viscosity, resin advancement, heat transfer
within the component/tool assembly during processing and preform compaction.
Formulations of the resin flow problem are given using the finite element/control volume
technique based on Darcy's Law of flow through porous media. This technique allows for
the efficient numerical calculation of the advancing resin front within the preform materials.
The heat transfer in the fabric preform and tooling is analyzed using a transient finite
element method which included the effects of convection on the tooling surfaces. Compaction
behavior of the tooling assembly is analyzed using a simplified isotropic form of the plane elasticity equations. All of these solutions were coupled together in a quasisteady
state non-linear fashion inside the computer code.
Advisors/Committee Members: Loos, Alfred C. (committeechair), Griffin, Odis Hayden Jr. (committee member), Ragab, Saad A. (committee member).
Subjects/Keywords: Composite materials; LD5655.V855 1994.M3365
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APA (6th Edition):
MacRae, J. D. (1994). Development and verification of a resin film infusion/resin transfer molding simulation model for fabrication of advanced textile composites. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/42574
Chicago Manual of Style (16th Edition):
MacRae, John Douglas. “Development and verification of a resin film infusion/resin transfer molding simulation model for fabrication of advanced textile composites.” 1994. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/42574.
MLA Handbook (7th Edition):
MacRae, John Douglas. “Development and verification of a resin film infusion/resin transfer molding simulation model for fabrication of advanced textile composites.” 1994. Web. 17 Apr 2021.
Vancouver:
MacRae JD. Development and verification of a resin film infusion/resin transfer molding simulation model for fabrication of advanced textile composites. [Internet] [Masters thesis]. Virginia Tech; 1994. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/42574.
Council of Science Editors:
MacRae JD. Development and verification of a resin film infusion/resin transfer molding simulation model for fabrication of advanced textile composites. [Masters Thesis]. Virginia Tech; 1994. Available from: http://hdl.handle.net/10919/42574
Virginia Tech
7.
Henderson, Joseph Lynn.
Combined structural and manufacturing optimization of stiffened composite panels.
Degree: MS, Aerospace Engineering, 1996, Virginia Tech
URL: http://hdl.handle.net/10919/44819
► Manufacturing considerations have been incorporated into the design optimization of a blade-stiffened composite panel. For the manufacturing analysis, a one-dimensional resin film infusion model…
(more)
▼ Manufacturing considerations have been incorporated into the design optimization
of a blade-stiffened composite panel. For the manufacturing analysis, a one-dimensional
resin film infusion model is developed to compute the infiltration time of the resin into a
fabric preform of the panel. Results are presented showing the effects of structurally
important design variables, such as cross-sectional geometry and material properties, on
the manufacturing performance of the panel. In addition, the effects of manufacturing
process variables, such as pressure and temperature, on the structural performance are
studied. The structural problem is formulated to minimize the panel mass subject to
buckling constraints. A simplified buckling analysis model for the panel is used to
compute the critical buckling loads. The objective of the manufacturing problem is to
minimize the resin infiltration time. Optimum panel designs for the manufacturing and
structures problems alone, as well as for the combined problem, are generated using a
genetic algorithm. These results indicate a strong connection between the structures and
manufacturing design variables and trade-offs between the responses, illustrating that a
multidisciplinary approach to the problem is essential to incorporating manufacturing into
the preliminary design stage.
Advisors/Committee Members: Loos, Alfred C. (committee member), Johnson, Eric R. (committee member), Gürdal, Zafer (committeecochair).
Subjects/Keywords: composites; structures; manufacturing; design optimization; genetic algorithms; stiffened panels; LD5655.V855 1996.H463
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APA (6th Edition):
Henderson, J. L. (1996). Combined structural and manufacturing optimization of stiffened composite panels. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/44819
Chicago Manual of Style (16th Edition):
Henderson, Joseph Lynn. “Combined structural and manufacturing optimization of stiffened composite panels.” 1996. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/44819.
MLA Handbook (7th Edition):
Henderson, Joseph Lynn. “Combined structural and manufacturing optimization of stiffened composite panels.” 1996. Web. 17 Apr 2021.
Vancouver:
Henderson JL. Combined structural and manufacturing optimization of stiffened composite panels. [Internet] [Masters thesis]. Virginia Tech; 1996. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/44819.
Council of Science Editors:
Henderson JL. Combined structural and manufacturing optimization of stiffened composite panels. [Masters Thesis]. Virginia Tech; 1996. Available from: http://hdl.handle.net/10919/44819
Virginia Tech
8.
Fingerson, John C.
Verification of a three-dimensional resin transfer molding process simulation model.
Degree: MS, Engineering Mechanics, 1995, Virginia Tech
URL: http://hdl.handle.net/10919/40857
► Experimental evidence was obtained to complete the verification of the parameters needed for input to a three-dimensional finite element model simulating the resin flow…
(more)
▼ Experimental evidence was obtained to complete the verification of the parameters
needed for input to a three-dimensional finite element model simulating the resin flow and
cure through an orthotropic fabric preform. The material characterizations completed
include resin kinetics and viscosity models, as well as preform permeability and
compaction models.
The steady-state and advancing front permeability measurement methods are
compared. The results indicate that both methods yield similar permeabilities for a plain
weave, bi-axial fiberglass fabric. Also, a method to determine principal directions and
permeabilities is discussed and results are shown for a multi-axial warp knit preform.
The flow of resin through a blade-stiffened preform was modeled and experiments
were completed to verify the results. The predicted inlet pressure was approximately 65%
of the measured value. A parametric study was performed to explain differences in
measured and predicted flow front advancement and inlet pressures.
Furthermore, PR-500 epoxy resinlIM7 8HS carbon fabric flat panels were fabricated
by the Resin Trat;lsfer Molding process. Tests were completed utilizing both perimeter
injection and center-port injection as resin inlet boundary conditions. The mold was
instrumented with FDEMS sensors, pressure transducers, and thermocouples to monitor
the process conditions. Results include a comparison of predicted and measured inletpressures and flow front position. For the perimeter injection case, the measured inlet
pressure and flow front results compared well to the predicted results. The results of the
center-port injection case showed that the predicted inlet pressure was approximately 50%
of the measured inlet pressure. Also, measured flow front position data did not agree well
with the predicted results. Possible reasons for error include fiber deformation at the resin
inlet and a lag in FDEMS sensor wet-out due to low mold pressures.
Advisors/Committee Members: Loos, Alfred C. (committeechair), Morris, Don H. (committee member), Hendricks, Scott L. (committee member).
Subjects/Keywords: resin molding process; LD5655.V855 1995.F564
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APA (6th Edition):
Fingerson, J. C. (1995). Verification of a three-dimensional resin transfer molding process simulation model. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/40857
Chicago Manual of Style (16th Edition):
Fingerson, John C. “Verification of a three-dimensional resin transfer molding process simulation model.” 1995. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/40857.
MLA Handbook (7th Edition):
Fingerson, John C. “Verification of a three-dimensional resin transfer molding process simulation model.” 1995. Web. 17 Apr 2021.
Vancouver:
Fingerson JC. Verification of a three-dimensional resin transfer molding process simulation model. [Internet] [Masters thesis]. Virginia Tech; 1995. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/40857.
Council of Science Editors:
Fingerson JC. Verification of a three-dimensional resin transfer molding process simulation model. [Masters Thesis]. Virginia Tech; 1995. Available from: http://hdl.handle.net/10919/40857
Virginia Tech
9.
Lu, Yunkai.
Mechanical Properties of Random Discontinuous Fiber Composites Manufactured from Wetlay Process.
Degree: MS, Engineering Science and Mechanics, 2002, Virginia Tech
URL: http://hdl.handle.net/10919/34503
► The random discontinuous fiber composite has uniform properties in all directions. The wetlay process is an efficient method to manufacture random discontinuous thermoplastic preform sheets…
(more)
▼ The random discontinuous fiber composite has uniform properties in all directions. The wetlay process is an efficient method to manufacture random discontinuous thermoplastic preform sheets that can be molded into random composite plaques in the hot-press. Investigations were done on the molding parameters that included the set-point mold pressure, set-point mold temperature and cooling methods. The fibers used in the study included glass and carbon fiber. Polypropylene (PP) and Polyethylene Terephthalate (PET) were used as the matrix.
Glass/PP and Glass/PET plaques that had fiber volume fractions ranging from 0.05 to 0.50 at an increment of 0.05 were molded. Both tensile and flexural tests were conducted. The test results showed a common pattern, i.e., the modulus and strength of the composite increased with the fiber volume fraction to a maximum and then started to descend. The test results were analyzed to find out the optimal fiber volume fraction that yielded the maximum modulus or strength. Carbon/PET composites plaques were also molded to compare their properties with Glass/PET composite at similar fiber volume fractions. Micrographs were taken of selected specimens to examine the internal structure of the material.
Existing micromechanics models that predict the tensile modulus or strength of random fiber composites were examined. Predictions from some of the models were compared with test data.
Advisors/Committee Members: Loos, Alfred C. (committeechair), Batra, Romesh C. (committee member), Hyer, Michael W. (committee member).
Subjects/Keywords: micromechanics; molding cycle; discontinuous; fiber reinforced composite; random; wetlay process
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APA (6th Edition):
Lu, Y. (2002). Mechanical Properties of Random Discontinuous Fiber Composites Manufactured from Wetlay Process. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/34503
Chicago Manual of Style (16th Edition):
Lu, Yunkai. “Mechanical Properties of Random Discontinuous Fiber Composites Manufactured from Wetlay Process.” 2002. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/34503.
MLA Handbook (7th Edition):
Lu, Yunkai. “Mechanical Properties of Random Discontinuous Fiber Composites Manufactured from Wetlay Process.” 2002. Web. 17 Apr 2021.
Vancouver:
Lu Y. Mechanical Properties of Random Discontinuous Fiber Composites Manufactured from Wetlay Process. [Internet] [Masters thesis]. Virginia Tech; 2002. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/34503.
Council of Science Editors:
Lu Y. Mechanical Properties of Random Discontinuous Fiber Composites Manufactured from Wetlay Process. [Masters Thesis]. Virginia Tech; 2002. Available from: http://hdl.handle.net/10919/34503
Virginia Tech
10.
Gonzalez-Ibarra, Alvaro.
The effects of polymeric binders on the processability and properties of composites made by suspension prepregging.
Degree: MS, Chemical Engineering, 1993, Virginia Tech
URL: http://hdl.handle.net/10919/44873
► This thesis concerns the production of thermoplastic/carbon fiber composites via aqueous suspension prepregging. Suspension prepregging requires the use of a binder dispersant: i) to…
(more)
▼ This thesis concerns the production of thermoplastic/carbon fiber composites
via aqueous suspension prepregging. Suspension prepregging requires the use of a
binder dispersant: i) to disperse the polymer particles so as to get good fiber-matrix
distribution in the prepreg, and ii) to improve the handling characteristics of the
prepreg, by holding the matrix to the fibers and the fibers to themselves. The effects of
the binder on the processability, properties, and performance of composites were
assessed.
It was found that the addition of the binder can affect both the matrix and the
composite performance depending on the binder concentration and chemistry. For
example an increase of 250 % on the complex dynamic viscosity of LaRC TPI matrix
was measured upon the addition of 21.3 wt% of imidized LaRC TPI polyamic acid
binder at a frequency of 1 Hz. The greatest fiber-matrix adhesion was observed for
PEEK composites when BisP BTDA polyamic acid was used as a binder.
A preliminary, qualitative study on the possibility of using suspension
prepregging as means of manufacturing thermoplastic/carbon fabric composites was
performed. Good penetration of PEEK polymer particles into the fabric was obtained
when the fabric was previously desized by acid digestion.
A preliminary study was made on the binding and dispersing capabilities of a
novel copolymer poly(pyridine ether-eo-ether ether ketone). The addition of the
copolymer to PEEK drastically increased the melt viscosity due to an ionomer effect.
This resulted in poorly consolidated panels with high void volumes.
Advisors/Committee Members: Davis, Richey M. (committeechair), Wightman, James P. (committee member), Loos, Alfred C. (committee member).
Subjects/Keywords: Suspensions (Chemistry); LD5655.V855 1993.G662
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APA (6th Edition):
Gonzalez-Ibarra, A. (1993). The effects of polymeric binders on the processability and properties of composites made by suspension prepregging. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/44873
Chicago Manual of Style (16th Edition):
Gonzalez-Ibarra, Alvaro. “The effects of polymeric binders on the processability and properties of composites made by suspension prepregging.” 1993. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/44873.
MLA Handbook (7th Edition):
Gonzalez-Ibarra, Alvaro. “The effects of polymeric binders on the processability and properties of composites made by suspension prepregging.” 1993. Web. 17 Apr 2021.
Vancouver:
Gonzalez-Ibarra A. The effects of polymeric binders on the processability and properties of composites made by suspension prepregging. [Internet] [Masters thesis]. Virginia Tech; 1993. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/44873.
Council of Science Editors:
Gonzalez-Ibarra A. The effects of polymeric binders on the processability and properties of composites made by suspension prepregging. [Masters Thesis]. Virginia Tech; 1993. Available from: http://hdl.handle.net/10919/44873
Virginia Tech
11.
Schultz, Marc Robert.
Energy Absorption Capacity of Graphite-Epoxy Composite Tubes.
Degree: MS, Engineering Mechanics, 1998, Virginia Tech
URL: http://hdl.handle.net/10919/35597
► The energy absorption capacity of a series of axially crushed composite tubes fabricated from high tow count graphite fiber is compared with those of similar…
(more)
▼ The energy absorption capacity of a series of axially crushed composite tubes fabricated from high tow count graphite fiber is compared with those of similar tubes fabricated from aerospace-grade fiber to determine the viability of considering the use of such fibers in automotive applications. To that end, graphite-epoxy tubular specimens with circular and square cross-sectional geometries; stacking sequences with ±45° fibers and with both ±45° and 0° fibers; and two different fiber types were fabricated and crushed both statically and dynamically to examine the energy absorption characteristics. The fiber types, in the form of preimpregnated tow (towpreg) from Thiokol, were Akzo Fortafil 50k fiber and aerospace-grade T300 12k fiber. Using the towpreg, sixteen tubes were filament wound on aluminum mandrels. Three specimens were cut from each of these tubes for a total of forty-eight specimens. Twenty-four of these specimens were crushed statically in a load frame and twenty-four were crushed dynamically in a drop fixture. In order to characterize the tubes and specimens, a number of measurements were taken. These measurements included length, wall thickness, cross-sectional dimensions, volume, and mass. Two important energy absorption measures were examined: the specific energy absorption (SEA) and the ratio of the peak load to the average load. The geometry had a significant effect on the energy absorption but the stacking sequence did not. It was also found that the 50k material was less effective at absorbing energy than the 12k material, but the 50k still may be acceptable.
Advisors/Committee Members: Hyer, Michael W. (committeechair), Lesko, John Jack (committee member), Loos, Alfred C. (committee member).
Subjects/Keywords: static; dynamic; low-cost; filament winding; towpreg; 12k; 50k
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APA (6th Edition):
Schultz, M. R. (1998). Energy Absorption Capacity of Graphite-Epoxy Composite Tubes. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/35597
Chicago Manual of Style (16th Edition):
Schultz, Marc Robert. “Energy Absorption Capacity of Graphite-Epoxy Composite Tubes.” 1998. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/35597.
MLA Handbook (7th Edition):
Schultz, Marc Robert. “Energy Absorption Capacity of Graphite-Epoxy Composite Tubes.” 1998. Web. 17 Apr 2021.
Vancouver:
Schultz MR. Energy Absorption Capacity of Graphite-Epoxy Composite Tubes. [Internet] [Masters thesis]. Virginia Tech; 1998. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/35597.
Council of Science Editors:
Schultz MR. Energy Absorption Capacity of Graphite-Epoxy Composite Tubes. [Masters Thesis]. Virginia Tech; 1998. Available from: http://hdl.handle.net/10919/35597
Virginia Tech
12.
Jackson, Mitchell L.
Modeling the microwave frequency permittivity of thermoplastic composite materials.
Degree: MS, Engineering Mechanics, 1993, Virginia Tech
URL: http://hdl.handle.net/10919/43420
► Mixture models were studied in an effort to predict the microwave frequency permittivities of unidirectional-fiber-reinforced thermoplastic-matrix composite materials as a function of fiber volume…
(more)
▼
Mixture models were studied in an effort to predict the
microwave frequency permittivities of unidirectional-fiber-reinforced
thermoplastic-matrix composite materials as a
function of fiber volume fraction, fiber orientation relative
to the electric field, and temperature. The permittivities
of the constituent fiber and plastic materials were measured
using a resonant cavity perturbation technique at 9.4 GHz and
2.45 GHz. The permittivities of the composite specimens were
measured using a reflection cavity technique at 9.4 GHz and
2.45 GHz. Simple" rule of -mixtures II models that use the
fiber and plastic permittivities have been found to
approximate the complex dielectric properties of the
composite for varied fiber volume fractions. The
permittivities of oriented composites were successfully
modeled at 9.4 GHz using a tensor rotation procedure.
Composite permittivities were modeled with temperature up to
the glass transition temperature of the thermoplastic matrix.
Good agreement was found between the mixture model and
experimental results for permittivity as a function of
temperature at 9.4 GHz.
Advisors/Committee Members: Stern, Curtis H. (committeechair), Kriz, Ronald D. (committee member), Loos, Alfred C. (committee member).
Subjects/Keywords: Microwave heating; LD5655.V855 1993.J224
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APA (6th Edition):
Jackson, M. L. (1993). Modeling the microwave frequency permittivity of thermoplastic composite materials. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/43420
Chicago Manual of Style (16th Edition):
Jackson, Mitchell L. “Modeling the microwave frequency permittivity of thermoplastic composite materials.” 1993. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/43420.
MLA Handbook (7th Edition):
Jackson, Mitchell L. “Modeling the microwave frequency permittivity of thermoplastic composite materials.” 1993. Web. 17 Apr 2021.
Vancouver:
Jackson ML. Modeling the microwave frequency permittivity of thermoplastic composite materials. [Internet] [Masters thesis]. Virginia Tech; 1993. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/43420.
Council of Science Editors:
Jackson ML. Modeling the microwave frequency permittivity of thermoplastic composite materials. [Masters Thesis]. Virginia Tech; 1993. Available from: http://hdl.handle.net/10919/43420
Virginia Tech
13.
Gandhe, Gajanan V.
Impact response of interleaved composite materials.
Degree: MS, Engineering Mechanics, 1988, Virginia Tech
URL: http://hdl.handle.net/10919/43859
► The need for better impact resistant composites has resulted in the development of many toughened resin systems. A combination of a tougher resin system along…
(more)
▼ The need for better impact resistant composites has resulted in the development of many toughened resin systems. A combination of a tougher resin system along with higher strength fibers increases the impact resistance of the composite. The use of an adhesive layer between two plies of the improved prepreg system has been found to considerably increase the impact resistance. This concept is known as "Interleafing."
This investigation studies the response of the interleaf materials to instrumented drop weight impact as compared with the response of non-interleaved materials. Two non-destructive quality evaluation techniques, namely, ultrasonics and eddy currents, are used to qualitatively evaluate the damage developed in the specimens. Several different energy levels of damage are studied.
The interleaved laminate had significantly better impact response than the non-interleaved laminate for the same impact energy. The onset of delamination was delayed by the use of the interleaf. Whereas damage could be detected at an impact energy as low as 1.75 ft-lb in the baseline laminate; the interleaved laminate did not show any ultrasonic
C-scan indication up to an impact of 2.45 ft-lb. The increase of delamination with increasing impact energy was slower in the interleaved specimen.
The eddy current method is not effective in detecting damage in the interleaved laminate because of the shielding effect of the interleaf. Compression Strength After Impact (CSAI) could not be used for the test laminates in this project, but the Tensile Strength After Impact test provided useful results. The tensile strength after impact of the interleaved specimen was between 20%-80% more than the baseline laminate up to impact energy of 10 ft-lb. The advantage of the interleaved specimen reduced at higher energy levels of impact.
Advisors/Committee Members: Griffin, Odis Hayden Jr. (committeechair), Henneke, Edmund G. II (committee member), Loos, Alfred C. (committee member).
Subjects/Keywords: Reinforced plastics; LD5655.V855 1988.G353
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APA (6th Edition):
Gandhe, G. V. (1988). Impact response of interleaved composite materials. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/43859
Chicago Manual of Style (16th Edition):
Gandhe, Gajanan V. “Impact response of interleaved composite materials.” 1988. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/43859.
MLA Handbook (7th Edition):
Gandhe, Gajanan V. “Impact response of interleaved composite materials.” 1988. Web. 17 Apr 2021.
Vancouver:
Gandhe GV. Impact response of interleaved composite materials. [Internet] [Masters thesis]. Virginia Tech; 1988. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/43859.
Council of Science Editors:
Gandhe GV. Impact response of interleaved composite materials. [Masters Thesis]. Virginia Tech; 1988. Available from: http://hdl.handle.net/10919/43859
Virginia Tech
14.
Song, Xiaolan.
Modeling of Thermoplastic Composite Filament Winding.
Degree: MS, Engineering Mechanics, 2000, Virginia Tech
URL: http://hdl.handle.net/10919/35370
► Thermoplastic composite filament winding is an on-line consolidation process, where the composite experiences a complex temperature history and undergoes a number of temperature history…
(more)
▼ Thermoplastic composite filament winding is an on-line consolidation process, where the composite experiences a complex temperature history and undergoes a number of temperature history affected microstructural changes that influence the structure's subsequent properties. These changes include melting, crystallization, void formation, degradation and consolidation. In the present study, models of the thermoplastic filament winding process were developed to identify and understand the relationships between process variables and the structure quality. These include models that describe the heat transfer, consolidation and crystallization processes that occur during fabrication of a filament wound composites structure.
A comprehensive thermal model of the thermoplastic filament winding process was developed to calculate the temperature profiles in the composite substrate and the towpreg temperature before entering the nippoint. A two-dimensional finite element heat transfer analysis for the composite-mandrel assembly was formulated in the polar coordinate system, which facilitates the description of the geometry and the boundary conditions. A four-node 'sector element' was used to describe the domain of interest. Sector elements were selected to give a better representation of the curved boundary shape which should improve accuracy with fewer elements compared to a finite element solution in the Cartesian-coordinate system. Hence the computational cost will be reduced. The second thermal analysis was a two-dimensional, Cartesian coordinate, finite element model of the towpreg as it enters the nippoint. The results show that the calculated temperature distribution in the composite substrate compared well with temperature data measured during winding and consolidation. The analysis also agrees with the experimental observation that the melt region is formed on the surface of the incoming towpreg in the nippoint and not on the substrate.
Incorporated with the heat transfer analysis were the consolidation and crystallization models. These models were used to calculate the degree of interply bonding and the crystallinity achieved during composite manufacture. Bonding and crystallinity developments during the winding process were investigated using the model. It is concluded that lower winding speed, higher hot-air heater nozzle temperature, and higher substrate preheating temperature yield higher nippoint temperature, better consolidation and a higher degree of crystallization. Complete consolidation and higher matrix crystallization will result in higher interlaminar strength of the wound composite structure.
Advisors/Committee Members: Loos, Alfred C. (committeechair), Gürdal, Zafer (committee member), Batra, Romesh C. (committee member).
Subjects/Keywords: Thermoplastic composite filament winding; on-line connsolidation; modeling
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APA (6th Edition):
Song, X. (2000). Modeling of Thermoplastic Composite Filament Winding. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/35370
Chicago Manual of Style (16th Edition):
Song, Xiaolan. “Modeling of Thermoplastic Composite Filament Winding.” 2000. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/35370.
MLA Handbook (7th Edition):
Song, Xiaolan. “Modeling of Thermoplastic Composite Filament Winding.” 2000. Web. 17 Apr 2021.
Vancouver:
Song X. Modeling of Thermoplastic Composite Filament Winding. [Internet] [Masters thesis]. Virginia Tech; 2000. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/35370.
Council of Science Editors:
Song X. Modeling of Thermoplastic Composite Filament Winding. [Masters Thesis]. Virginia Tech; 2000. Available from: http://hdl.handle.net/10919/35370
Virginia Tech
15.
Myslinski, Paul Joseph.
Analysis of Cyanate Ester Resins and Graphite Fabric for Use in Resin Film Infusion Processing.
Degree: MS, Materials Science and Engineering, 1997, Virginia Tech
URL: http://hdl.handle.net/10919/35804
► The objective of this investigation was to characterize two cyanate ester resins and a eight harness satin (8HS) graphite fabric for use in resin film…
(more)
▼ The objective of this investigation was to characterize two cyanate ester resins and a eight harness satin (8HS) graphite fabric for use in resin film infusion (RFI) processing. Two cyanate ester resin systems were characterized to determine their cure-kinetics, and viscosities during cure. A 8HS graphite fabric was tested in compaction and through the thickness permeability. A one-dimensional, through the thickness, flow and cure computer simulation was run.
The resin cure-kinetics models predicted the curing behavior of the resins as functions of time, temperature, and degree of cure. The proposed viscosity models determined the resin viscosity as a function of temperature and degree of cure. The 8HS graphite fabric was tested in compaction and through the thickness permeability to determine the effect of compaction pressure on fiber volume fraction and in turn on through the thickness permeability. The one-dimensional RFI flow and cure simulation combined the cure-kinetics and viscosity models of the resins with the characteristics of the graphite fabric and determined resin infiltration and cure times.
The proposed cure-kinetics and viscosity models were more than adequate in modeling the cure and flow behavior of the cyanate ester resin systems. Power law curve fits accurately represented the compaction and through the thickness permeability of the 8HS graphite fabric. Finally, the one-dimensional RFI flow and cure simulation showed that resin viscosity was the major influence on the infiltration times.
Advisors/Committee Members: Loos, Alfred C. (committeechair), Love, Brian J. (committee member), Kander, Ronald C. (committee member).
Subjects/Keywords: Graphite Fiber Composites; Cure-Kinetics; Cyanate Esters; Resin Film Infusion
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APA (6th Edition):
Myslinski, P. J. (1997). Analysis of Cyanate Ester Resins and Graphite Fabric for Use in Resin Film Infusion Processing. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/35804
Chicago Manual of Style (16th Edition):
Myslinski, Paul Joseph. “Analysis of Cyanate Ester Resins and Graphite Fabric for Use in Resin Film Infusion Processing.” 1997. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/35804.
MLA Handbook (7th Edition):
Myslinski, Paul Joseph. “Analysis of Cyanate Ester Resins and Graphite Fabric for Use in Resin Film Infusion Processing.” 1997. Web. 17 Apr 2021.
Vancouver:
Myslinski PJ. Analysis of Cyanate Ester Resins and Graphite Fabric for Use in Resin Film Infusion Processing. [Internet] [Masters thesis]. Virginia Tech; 1997. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/35804.
Council of Science Editors:
Myslinski PJ. Analysis of Cyanate Ester Resins and Graphite Fabric for Use in Resin Film Infusion Processing. [Masters Thesis]. Virginia Tech; 1997. Available from: http://hdl.handle.net/10919/35804
Virginia Tech
16.
Steward, Scott D.
The Effect of Salt Splash on Nylon 6,6.
Degree: MS, Materials Science and Engineering, 1999, Virginia Tech
URL: http://hdl.handle.net/10919/35635
► One of the most common environmental exposures that nylon undergoes, when used for automotive applications, is that of salt splash, which commonly occurs during winter…
(more)
▼ One of the most common environmental exposures that nylon undergoes, when used for automotive applications, is that of salt splash, which commonly occurs during winter driving. This study looks at the effect of various salts (NaCl, KCl, CaCl2) on the thermal and mechanical properties of nylon when exposed to one and four molar aqueous salt solutions. It was found that the diffusion of salt solutions into nylon 6,6 occurred in a pseudo-Fickian manner. Also, it was found that the presence of salt had an effect on the rate of decrease of yield stress with increasing exposure time. The presence of residual salt was found to accelerated deterioration of nylon 6,6, possibly via hydrolysis. In addition, it was found that residual salt was left after water was removed from the system and that this salt was removable.
Advisors/Committee Members: Kander, Ronald G. (committeechair), Love, Brian J. (committee member), Loos, Alfred C. (committee member).
Subjects/Keywords: Moisture Absorption; Nylon; Salt Exposure
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APA (6th Edition):
Steward, S. D. (1999). The Effect of Salt Splash on Nylon 6,6. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/35635
Chicago Manual of Style (16th Edition):
Steward, Scott D. “The Effect of Salt Splash on Nylon 6,6.” 1999. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/35635.
MLA Handbook (7th Edition):
Steward, Scott D. “The Effect of Salt Splash on Nylon 6,6.” 1999. Web. 17 Apr 2021.
Vancouver:
Steward SD. The Effect of Salt Splash on Nylon 6,6. [Internet] [Masters thesis]. Virginia Tech; 1999. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/35635.
Council of Science Editors:
Steward SD. The Effect of Salt Splash on Nylon 6,6. [Masters Thesis]. Virginia Tech; 1999. Available from: http://hdl.handle.net/10919/35635
Virginia Tech
17.
Ogden, Andrea L.
The development and evaluation of an alternative powder prepregging technique for use with larc-tpi/graphite composites.
Degree: MS, Engineering Mechanics, 1991, Virginia Tech
URL: http://hdl.handle.net/10919/45252
Subjects/Keywords: Fibrous composites; LD5655.V855 1991.O543
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APA (6th Edition):
Ogden, A. L. (1991). The development and evaluation of an alternative powder prepregging technique for use with larc-tpi/graphite composites. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/45252
Chicago Manual of Style (16th Edition):
Ogden, Andrea L. “The development and evaluation of an alternative powder prepregging technique for use with larc-tpi/graphite composites.” 1991. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/45252.
MLA Handbook (7th Edition):
Ogden, Andrea L. “The development and evaluation of an alternative powder prepregging technique for use with larc-tpi/graphite composites.” 1991. Web. 17 Apr 2021.
Vancouver:
Ogden AL. The development and evaluation of an alternative powder prepregging technique for use with larc-tpi/graphite composites. [Internet] [Masters thesis]. Virginia Tech; 1991. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/45252.
Council of Science Editors:
Ogden AL. The development and evaluation of an alternative powder prepregging technique for use with larc-tpi/graphite composites. [Masters Thesis]. Virginia Tech; 1991. Available from: http://hdl.handle.net/10919/45252
Virginia Tech
18.
Grimsley, Brian William.
Characterization of the Vacuum Assisted Resin Transfer Molding Process for Fabrication of Aerospace Composites.
Degree: MS, Materials Science and Engineering, 2005, Virginia Tech
URL: http://hdl.handle.net/10919/36062
► This work was performed under a cooporative research effort sponsored by the National Aeronautics and Space Administration (NASA) in conjunction with the aerospace industry and…
(more)
▼ This work was performed under a cooporative research effort sponsored by the National Aeronautics and Space Administration (NASA) in conjunction with the aerospace industry and acedemia. One of the primary goals of NASA is to improve the safety and affordability of commercial air flight. Part of this goal includes research to reduce fuel consumption by developing lightweight carbon fiber, polymer matrix composites to replace existing metallic airframe structure. In the Twenty-first Aircraft Technology Program (TCAT) efforts were focused on developing novel processing methods to fabricate tailored composite airframe structure. The Vacuum Assisted Resin Transfer Molding (VARTM) processing technique offers a safer, more affordable alternative to manufacture large scale composite fuselages and wing structures. Vacuum assisted resin transfer molding is an infusion process originally developed for manufacturing of composites in the marine industry. The process is a variation of Resin Transfer Molding (RTM), where the rigid matched metal tooling is replaced on one side with a flexible vacuum bag. The entire process, including infusion and consolidation of the part, occurs at atmospheric pressure (101.5 kPa). High-performance composites with fiber volumes in the range of 45% to 50% can be achieved without the use of an autoclave. The main focus of the VARTM process development effort was to determine the feasibility of manufacturing aerospace quality composites with fiber volume fractions approaching 60%.
A science-based approach was taken, utilizing finite element process models to characterize and develop a full understanding of the VARTM infusion process as well as the interaction of the constituent materials. Achieving aerospace quality composites requires further development not only of the VARTM process, but also of the matrix resins and fiber preforms. The present work includes an investigation of recently developed epoxy matrix resins, including the characterization of the resin cure kinetics and flow behaviors. Two different fiber preform architectures were characterized to determine the response to compaction under VARTM conditions including a study to determine the effect of thickness on maximum achievable fiber volume fraction. Experiments were also conducted to determine the permeabilities of these preforms under VARTM flow conditions. Both the compaction response and the permeabilities of the preforms were fit to empirical models which can be used as input for future work to simulate VARTM infusion using process models.
Actual infusion experiments of these two types preforms were conducted using instrumented tools to determine the pressures and displacements that occur during VARTM infiltration. Flow experiments on glass tooling determined the fill-times and flow front evolution of preform specimens of various thicknesses. The results of these experiments can be used as validation of process model infusion simulations and to verify the compaction and permeability empirical models. Panels were infused with…
Advisors/Committee Members: Loos, Alfred C. (committeechair), Love, Brian J. (committee member), Hyer, Michael W. (committee member).
Subjects/Keywords: VARTM; Compaction; Infusion; Fiber-Preform; Permeability; Epoxy-Resin
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APA (6th Edition):
Grimsley, B. W. (2005). Characterization of the Vacuum Assisted Resin Transfer Molding Process for Fabrication of Aerospace Composites. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/36062
Chicago Manual of Style (16th Edition):
Grimsley, Brian William. “Characterization of the Vacuum Assisted Resin Transfer Molding Process for Fabrication of Aerospace Composites.” 2005. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/36062.
MLA Handbook (7th Edition):
Grimsley, Brian William. “Characterization of the Vacuum Assisted Resin Transfer Molding Process for Fabrication of Aerospace Composites.” 2005. Web. 17 Apr 2021.
Vancouver:
Grimsley BW. Characterization of the Vacuum Assisted Resin Transfer Molding Process for Fabrication of Aerospace Composites. [Internet] [Masters thesis]. Virginia Tech; 2005. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/36062.
Council of Science Editors:
Grimsley BW. Characterization of the Vacuum Assisted Resin Transfer Molding Process for Fabrication of Aerospace Composites. [Masters Thesis]. Virginia Tech; 2005. Available from: http://hdl.handle.net/10919/36062
Virginia Tech
19.
Caba, Aaron C. Jr.
Verification of a Three-Dimensional Resin Film Infusion Proecss Simulation Model.
Degree: MS, Engineering Science and Mechanics, 1998, Virginia Tech
URL: http://hdl.handle.net/10919/36572
► This investigation completed the verification of a three-dimensional resin transfer molding/resin film infusion (RTM/RFI) process simulation model. The model incorporates resin flow through an anisotropic…
(more)
▼ This investigation completed the verification of a three-dimensional resin transfer molding/resin film infusion (RTM/RFI) process simulation model. The model incorporates resin flow through an anisotropic carbon fiber preform, cure kinetics of the resin, and heat transfer within the preform/tool assembly. The computer model can predict the flow front location, resin pressure distribution, and thermal profiles in the modeled part.
The formulation for the flow model is given using the finite element/control volume (FE/CV) technique based on Darcy's Law of creeping flow through a porous media. The FE/CV technique is a numerically efficient method for finding the flow front location and the fluid pressure. The heat transfer model is based on the three-dimensional, transient heat conduction equation, including heat generation. Boundary conditions include specified temperature and convection. The code was designed with a modular approach so the flow and/or the thermal module may be turned on or off as desired. Both models are solved sequentially in a quasi-steady state fashion.
A mesh refinement study was completed on a one-element thick model to determine the recommended size of elements that would result in a converged model for a typical RFI analysis. Guidelines are established for checking the convergence of a model, and the recommended element sizes are listed.
Several experiments were conducted and computer simulations of the experiments were run to verify the simulation model. Isothermal, non-reacting flow in a T-stiffened section was simulated to verify the flow module. Predicted infiltration times were within 12-20 percent of measured times. The predicted pressures were approximately 50 percent of the measured pressures. A study was performed to attempt to explain the difference in pressures.
Non-isothermal experiments with a reactive resin were modeled to verify the thermal module and the resin model. Two panels were manufactured using the RFI process. One was a stepped panel and the other was a panel with two `T' stiffeners. The difference between the predicted infiltration times and the experimental times was 4 to 23 percent.
Advisors/Committee Members: Loos, Alfred C. (committeechair), Johnson, Eric R. (committee member), Batra, Romesh C. (committee member).
Subjects/Keywords: resin film infusion; resin transfer molding; composite manufacturing; simulation; modeling; textile preform; flow in porous media; heat transfer
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APA (6th Edition):
Caba, A. C. J. (1998). Verification of a Three-Dimensional Resin Film Infusion Proecss Simulation Model. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/36572
Chicago Manual of Style (16th Edition):
Caba, Aaron C Jr. “Verification of a Three-Dimensional Resin Film Infusion Proecss Simulation Model.” 1998. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/36572.
MLA Handbook (7th Edition):
Caba, Aaron C Jr. “Verification of a Three-Dimensional Resin Film Infusion Proecss Simulation Model.” 1998. Web. 17 Apr 2021.
Vancouver:
Caba ACJ. Verification of a Three-Dimensional Resin Film Infusion Proecss Simulation Model. [Internet] [Masters thesis]. Virginia Tech; 1998. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/36572.
Council of Science Editors:
Caba ACJ. Verification of a Three-Dimensional Resin Film Infusion Proecss Simulation Model. [Masters Thesis]. Virginia Tech; 1998. Available from: http://hdl.handle.net/10919/36572
Virginia Tech
20.
Cowan, Amy Lorraine.
Crack Path Bifurcation at a Tear Strap in a Pressurized Stiffened Cylindrical Shell.
Degree: MS, Aerospace and Ocean Engineering, 2002, Virginia Tech
URL: http://hdl.handle.net/10919/10027
► A finite element model of a fracture test specimen is developed using the STAGS computer code (STructural Analysis of General Shells). The test specimen was…
(more)
▼ A finite element model of a fracture test specimen is developed using the STAGS computer code (STructural Analysis of General Shells). The test specimen was an internally pressurized, aluminum cylindrical shell reinforced with two externally bonded aluminum tear straps around its circumference. The shell contained an initial, axial through-crack centered between the straps. The crack propagated slowly in the axial direction as the pressure increased above a certain value until a maximum pressure was attained, and then the crack propagated dynamically. The tear straps sufficiently toughened the shell such that the dynamic crack path bifurcated near the edges of the straps. The bifurcated crack branches ran circumferentially, parallel to the straps causing the shell wall to flap open.
The STAGS analysis for the static equilibrium configurations of the fractured shell include geometric nonlinearity and elastic-plastic material behavior. The crack tip opening angle (CTOA) is used in the criterion for ductile crack growth, and the critical value of the CTOA is determined by correlating the STAGS predictions of the stable portion of the crack growth curve (internal pressure versus half crack length) to the test. With the employment of a new STAGS algorithm, the complete axial crack growth curve, including both the stable and unstable portions, through the tear strap is obtained. The complete axial crack growth curve indicates that crack growth through the strap is unlikely. STAGS models with long cracks which bifurcate at various half crack lengths are developed to assess the location of crack bifurcation. Three different stress based crack turning criteria are investigated from the axial crack growth results as a second method for assessing a location of bifurcation. The bifurcation analyses and stress based turning criteria corroborate the experimentally measured bifurcation point. A parametric study is then conducted to determine the influence of tear strap thickness and width on the location of crack bifurcation.
Advisors/Committee Members: Johnson, Eric R. (committeechair), Kapania, Rakesh K. (committee member), Loos, Alfred C. (committee member).
Subjects/Keywords: tear strap; pressurized cylinder; crack bifurcation
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APA (6th Edition):
Cowan, A. L. (2002). Crack Path Bifurcation at a Tear Strap in a Pressurized Stiffened Cylindrical Shell. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/10027
Chicago Manual of Style (16th Edition):
Cowan, Amy Lorraine. “Crack Path Bifurcation at a Tear Strap in a Pressurized Stiffened Cylindrical Shell.” 2002. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/10027.
MLA Handbook (7th Edition):
Cowan, Amy Lorraine. “Crack Path Bifurcation at a Tear Strap in a Pressurized Stiffened Cylindrical Shell.” 2002. Web. 17 Apr 2021.
Vancouver:
Cowan AL. Crack Path Bifurcation at a Tear Strap in a Pressurized Stiffened Cylindrical Shell. [Internet] [Masters thesis]. Virginia Tech; 2002. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/10027.
Council of Science Editors:
Cowan AL. Crack Path Bifurcation at a Tear Strap in a Pressurized Stiffened Cylindrical Shell. [Masters Thesis]. Virginia Tech; 2002. Available from: http://hdl.handle.net/10919/10027
Virginia Tech
21.
Demaree, Robert John.
The effects of process parameters on the properties of resin transfer molded composites.
Degree: MS, Materials Science and Engineering, 1996, Virginia Tech
URL: http://hdl.handle.net/10919/45865
Subjects/Keywords: composite panel construction; LD5655.V855 1996.D463
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APA (6th Edition):
Demaree, R. J. (1996). The effects of process parameters on the properties of resin transfer molded composites. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/45865
Chicago Manual of Style (16th Edition):
Demaree, Robert John. “The effects of process parameters on the properties of resin transfer molded composites.” 1996. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/45865.
MLA Handbook (7th Edition):
Demaree, Robert John. “The effects of process parameters on the properties of resin transfer molded composites.” 1996. Web. 17 Apr 2021.
Vancouver:
Demaree RJ. The effects of process parameters on the properties of resin transfer molded composites. [Internet] [Masters thesis]. Virginia Tech; 1996. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/45865.
Council of Science Editors:
Demaree RJ. The effects of process parameters on the properties of resin transfer molded composites. [Masters Thesis]. Virginia Tech; 1996. Available from: http://hdl.handle.net/10919/45865
Virginia Tech
22.
Lombardi, Vincent T.
A layer tension loss and cure model for filament wound composites.
Degree: MS, Engineering Mechanics, 1991, Virginia Tech
URL: http://hdl.handle.net/10919/41679
► The simulation program FWCURE [1] models the curing process and layer tension loss of axisymmetric filament wound composite cases during fabrication. For a specified temperature…
(more)
▼ The simulation program FWCURE [1] models the curing process and layer tension loss of axisymmetric filament wound composite cases during fabrication. For a specified temperature cure cycle, the model predicts the temperature distribution, resin degree of cure, viscosity, layer compaction, and fiber motion throughout the composite case during cure. The scope of the simulation program developed by Tzeng [1] has been extended, and the modifications to the FWCURE program are the goals of this investigation. Major modifications to FWCORE include a more general 2-D layer tension loss model, additions to an element curvature calculation routine, a new cure reaction kinetics model and viscosity model for a Fiberite-974 epoxy resin system, and modifications and additions to Input/Output (I/O) throughout the program. Modifications and additions to FWCORE are implemented in the analysis of an 18 inch diameter test bottle. Results of the simulation are compared with test data obtained during winding and cure of a graphite-epoxy 18 inch test bottle. Excellent agreement was obtained between the results of the model and data. Another major accomplishment involved coupling FWCURE with a thermo-mechanical stress simulation program called WACSAFE. When combined, the coupled program forms an improved comprehensive structural model which characterizes the thermal, chemical, physical, and mechanical processes occurring during winding and cure of filament wound composite cases. The complete simulation program should provide the process engineer with a resource to help select an optimum fabrication cycle, assess the processing characteristics of new matrix reein eystems, and act as a simulator to yield real time, closed loop process control. FWCURE should also provide information on the processing parameters that have the greatest effect on the final filament wound composite structure.
Advisors/Committee Members: Loos, Alfred C. (committeechair), Knight, Charles E. (committee member), Grant, J. Walter (committee member).
Subjects/Keywords: Fibrous composites; LD5655.V855 1991.L672
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APA (6th Edition):
Lombardi, V. T. (1991). A layer tension loss and cure model for filament wound composites. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/41679
Chicago Manual of Style (16th Edition):
Lombardi, Vincent T. “A layer tension loss and cure model for filament wound composites.” 1991. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/41679.
MLA Handbook (7th Edition):
Lombardi, Vincent T. “A layer tension loss and cure model for filament wound composites.” 1991. Web. 17 Apr 2021.
Vancouver:
Lombardi VT. A layer tension loss and cure model for filament wound composites. [Internet] [Masters thesis]. Virginia Tech; 1991. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/41679.
Council of Science Editors:
Lombardi VT. A layer tension loss and cure model for filament wound composites. [Masters Thesis]. Virginia Tech; 1991. Available from: http://hdl.handle.net/10919/41679
Virginia Tech
23.
Call, Russell Kent.
Parameter establishment and verification of a fabrication stress model and a thermo-kinetic cure model for filament wound structures.
Degree: MS, Engineering Mechanics, 1991, Virginia Tech
URL: http://hdl.handle.net/10919/44209
► Two comprehensive composite fabrication simulation computer codes have been written. These codes when coupled together have the capability to model the filament winding and curing…
(more)
▼ Two comprehensive composite fabrication simulation computer codes have been written. These codes when coupled together have the capability to model the filament winding and curing
processes for composite structures. The "Filament Winding Cure" (FWCURE) code is a thermo-kinetic model. FWCURE models the resin viscosity, percent of cure, temperature, resin flow, and layer location. As these characteristics change, they have an effect on the fiber tension within the
composite. The "Winding and Curing Stress Analysis Finite Element" (WACSAFE) code models the filament winding process and predicts manufacturing stresses and strains based on material properties, lay-down tension and wind angle.
The permeability model in FWCURE requires constants that are found experimentally. The WACSAFE code requires an input tension that is equivalent to the initial spool tension minus the instantaneous tension losses.
The permeability constants and the instantaneous tension losses were found experimentally. The codes were then used to predict fiber tension, tension losses and mandrel strains for experimental test cylinders. The predictions were compared to test data.
Advisors/Committee Members: Loos, Alfred C. (committeechair), Knight, Charles E. (committee member), Griffin, Odis Hayden Jr. (committee member).
Subjects/Keywords: Fibrous composites; LD5655.V855 1991.C344
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APA (6th Edition):
Call, R. K. (1991). Parameter establishment and verification of a fabrication stress model and a thermo-kinetic cure model for filament wound structures. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/44209
Chicago Manual of Style (16th Edition):
Call, Russell Kent. “Parameter establishment and verification of a fabrication stress model and a thermo-kinetic cure model for filament wound structures.” 1991. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/44209.
MLA Handbook (7th Edition):
Call, Russell Kent. “Parameter establishment and verification of a fabrication stress model and a thermo-kinetic cure model for filament wound structures.” 1991. Web. 17 Apr 2021.
Vancouver:
Call RK. Parameter establishment and verification of a fabrication stress model and a thermo-kinetic cure model for filament wound structures. [Internet] [Masters thesis]. Virginia Tech; 1991. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/44209.
Council of Science Editors:
Call RK. Parameter establishment and verification of a fabrication stress model and a thermo-kinetic cure model for filament wound structures. [Masters Thesis]. Virginia Tech; 1991. Available from: http://hdl.handle.net/10919/44209
Virginia Tech
24.
Goodman, Kendall E.
Thermoplastic prepreg manufacture by solution impregnation.
Degree: MS, Engineering Mechanics, 1990, Virginia Tech
URL: http://hdl.handle.net/10919/42197
► Advanced thermoplastic composites are commonly manufactured from "'prepreg" materials, where the reinforcing fibers are preimpregnated with resin. The objectives of this investigation were to…
(more)
▼
Advanced thermoplastic composites are commonly manufactured from "'prepreg" materials,
where the reinforcing fibers are preimpregnated with resin. The objectives of this investigation
were to identify the critical parameters in impregnation of the fiber tow by a
thermoplastic solution, and to produce high quality thermoplastic prepreg.
Continuous carbon fibers (AS4 and AU4) were impregnated with a thermoplastic resin
solution using a research scale, single tow, drum winding prepreg machine. The parameters
varied to control the degree of impregnation of the fiber tow were, weight percent polymer in
solution, die size, fiber tow tension, fiber tow velocity, and the use of impregnation pins.
These parameters were varied during the prepregging operation and prepreg samples
were evaluated to determine resin content. Viscosity studies were performed on the polymer
solutions by means of a Rheometrics Mechanical Spectrometer. Thermogravimetric analyses
were performed on the thermoplastic solution and the prepreg. Cross-sectional
photomicrographs were obtained to determine the degree of impregnation and the fiber/resin
distribution.
Unidirectional laminates were fabricated from the prepreg. Transverse tensile and
double cantilivered beam mechanical tests were performed. Fractography photomicrographs
were taken. X-Ray photoelectron spectroscopy was used to investigate the possibility of residual
solvent in the laminates.
High quality prepreg was manufactured and the critical parameters in the prepregging
process were identified and their effect on the prepreg was quantified.
Advisors/Committee Members: Loos, Alfred C. (committeechair), Reifsnider, Kenneth L. (committee member), Baird, Donald G. (committee member), Davis, Richey M. (committee member).
Subjects/Keywords: Thermoplastics; LD5655.V855 1990.G663
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APA (6th Edition):
Goodman, K. E. (1990). Thermoplastic prepreg manufacture by solution impregnation. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/42197
Chicago Manual of Style (16th Edition):
Goodman, Kendall E. “Thermoplastic prepreg manufacture by solution impregnation.” 1990. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/42197.
MLA Handbook (7th Edition):
Goodman, Kendall E. “Thermoplastic prepreg manufacture by solution impregnation.” 1990. Web. 17 Apr 2021.
Vancouver:
Goodman KE. Thermoplastic prepreg manufacture by solution impregnation. [Internet] [Masters thesis]. Virginia Tech; 1990. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/42197.
Council of Science Editors:
Goodman KE. Thermoplastic prepreg manufacture by solution impregnation. [Masters Thesis]. Virginia Tech; 1990. Available from: http://hdl.handle.net/10919/42197
Virginia Tech
25.
Thompson, Joseph E.
Compaction and Cure of Resin Film Infusion Prepregs.
Degree: MS, Engineering Science and Mechanics, 2004, Virginia Tech
URL: http://hdl.handle.net/10919/36479
► Gutowski et al.'s model has been employed to describe the cure and consolidation of prepregs used for resin film infusion. Resin kinetics, rheology, flow and…
(more)
▼ Gutowski et al.'s model has been employed to describe the cure and consolidation of prepregs used for resin film infusion. Resin kinetics, rheology, flow and fiber deformation are considered. Resin kinetics are simulated with an isothermal autocatalytic-1 type relation. The non-Newtonian viscosity of the Cytec™ 754 resin is represented with a gel type expression. The one dimensional flow of resin through a deformable, partially saturated porous medium is studied. A nonlinear partial differential equation describing the spatial and temporal variation of the fiber volume fraction combining the continuity equation, Darcy's Law, and mat compressibility has been derived and solved numerically. Resin is assumed to be incompressible and inertial effects are neglected. Based on the resin content of regions where resin and fiber coexist, expressions for tracking resin flow through fully and partially saturated regions of fiber are given. Values of material parameters for the E-QX 3600-5 glass fabric are estimated from literature data involving compression of similar dry fabrics and through comparison of computed results with the experimental data. Results for the final thickness of the consolidated part agree with the experimental values, but those for the mass loss do not.
Advisors/Committee Members: Batra, Romesh C. (committeechair), Loos, Alfred C. (committee member), Ragab, Saad A. (committee member), Case, Scott W. (committee member).
Subjects/Keywords: resin film infusion; kinetics; viscosity; Cytec 754; RFI; fiber compaction
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APA (6th Edition):
Thompson, J. E. (2004). Compaction and Cure of Resin Film Infusion Prepregs. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/36479
Chicago Manual of Style (16th Edition):
Thompson, Joseph E. “Compaction and Cure of Resin Film Infusion Prepregs.” 2004. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/36479.
MLA Handbook (7th Edition):
Thompson, Joseph E. “Compaction and Cure of Resin Film Infusion Prepregs.” 2004. Web. 17 Apr 2021.
Vancouver:
Thompson JE. Compaction and Cure of Resin Film Infusion Prepregs. [Internet] [Masters thesis]. Virginia Tech; 2004. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/36479.
Council of Science Editors:
Thompson JE. Compaction and Cure of Resin Film Infusion Prepregs. [Masters Thesis]. Virginia Tech; 2004. Available from: http://hdl.handle.net/10919/36479
Virginia Tech
26.
Girardin, Benoit.
Contact stress analysis and fatigue life prediction for a cam-roller follower system.
Degree: MS, Engineering Science and Mechanics, 1994, Virginia Tech
URL: http://hdl.handle.net/10919/44615
► An analytical treatment of the fatigue performance of a cam-roller followler system as influenced by residual stresses induced by grinding, is developed. An approach…
(more)
▼ An analytical treatment of the fatigue performance of a cam-roller followler system as
influenced by residual stresses induced by grinding, is developed. An approach based on an
extended Hertzian analysis is used to determine the 3-D contact stress fields, which are then
combined by elastic superposition with the residual stress fields. These residual stresses were
measured previously by the x-ray diffraction technique and represent a range of grinding protocols
from mild to abusive.
The maximum cyclic component, generally occurring subsurface, is then identified in
terms of an effective stress amplitude and mean which are used with a fatigue damage model to
predict fatigue crack initiation. Results, pending experimental confirmation, appear reasonable and
provide a useful basis for optimizing cam performance in terms of manufacturing and design
parameters.
Advisors/Committee Members: Landgraf, Ronald W. (committeechair), Meirovitch, Leonard (committee member), Loos, Alfred C. (committee member), Eiss, Norman S. Jr. (committee member).
Subjects/Keywords: fatigue life prediction; LD5655.V855 1994.G573
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APA (6th Edition):
Girardin, B. (1994). Contact stress analysis and fatigue life prediction for a cam-roller follower system. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/44615
Chicago Manual of Style (16th Edition):
Girardin, Benoit. “Contact stress analysis and fatigue life prediction for a cam-roller follower system.” 1994. Masters Thesis, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/44615.
MLA Handbook (7th Edition):
Girardin, Benoit. “Contact stress analysis and fatigue life prediction for a cam-roller follower system.” 1994. Web. 17 Apr 2021.
Vancouver:
Girardin B. Contact stress analysis and fatigue life prediction for a cam-roller follower system. [Internet] [Masters thesis]. Virginia Tech; 1994. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/44615.
Council of Science Editors:
Girardin B. Contact stress analysis and fatigue life prediction for a cam-roller follower system. [Masters Thesis]. Virginia Tech; 1994. Available from: http://hdl.handle.net/10919/44615
Virginia Tech
27.
Bucher, Richard A.
High performance thermoplastic matrix composite processing: dry powder prepregging, plasma treatment, consolidation/crystallization analysis.
Degree: PhD, Materials Engineering Science, 1994, Virginia Tech
URL: http://hdl.handle.net/10919/39541
► The quest for developing high performance materials, originally responsible for the birth and growth of the composites industry, is now responsible for the drive to…
(more)
▼ The quest for developing high performance materials, originally responsible for the birth and growth of the composites industry, is now responsible for the drive to produce composites which outperform those used today. A great deal of this interest lies in the use of thermoplastic polymers as the composite matrix. Thermoplastics offer the potential of improved mechanical performance, greater solvent resistance, better impact tolerance, as well as cost saving processing attributes such as infinite shelf life, the ability to be recycled, short processing time and repairability. Unfortunately, these advantages come at the expense of a very high melt viscosity which makes the prepregging process, where the fiber and polymer are combined, very difficult. To overcome this and associated difficulties a detailed analysis of thermoplastic matrix composite processing is developed.
The primary area of focus involves the development of an electrostatic dry polymer
powder prepregging facility. This unit is capable of the production of high quality towpreg from thermoplastic polymers and reinforcing fibers. Two approaches, statistical and stochastic, were employed to model the process of polymer deposition on the fibers in the prepregging process. These models are used to optimize the production of towpreg. A modification of the prepregging facility allows for the production of towpreg from very small (15 g) samples of polymer. This is extremely useful for analysis and performance verification of state of the art polymer systems.
Advisors/Committee Members: Loos, Alfred C. (committeechair), Davis, Richey M. (committee member), Reifsnider, Kenneth L. (committee member), Kander, Ronald C. (committee member), Wightman, James P. (committee member).
Subjects/Keywords: Thermoplastic composites; LD5655.V856 1994.B834
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APA (6th Edition):
Bucher, R. A. (1994). High performance thermoplastic matrix composite processing: dry powder prepregging, plasma treatment, consolidation/crystallization analysis. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/39541
Chicago Manual of Style (16th Edition):
Bucher, Richard A. “High performance thermoplastic matrix composite processing: dry powder prepregging, plasma treatment, consolidation/crystallization analysis.” 1994. Doctoral Dissertation, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/39541.
MLA Handbook (7th Edition):
Bucher, Richard A. “High performance thermoplastic matrix composite processing: dry powder prepregging, plasma treatment, consolidation/crystallization analysis.” 1994. Web. 17 Apr 2021.
Vancouver:
Bucher RA. High performance thermoplastic matrix composite processing: dry powder prepregging, plasma treatment, consolidation/crystallization analysis. [Internet] [Doctoral dissertation]. Virginia Tech; 1994. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/39541.
Council of Science Editors:
Bucher RA. High performance thermoplastic matrix composite processing: dry powder prepregging, plasma treatment, consolidation/crystallization analysis. [Doctoral Dissertation]. Virginia Tech; 1994. Available from: http://hdl.handle.net/10919/39541
Virginia Tech
28.
Subramanian, Suresh.
Effect of fiber/Matrix Interphase on the Long Term Behavior of Cross-Ply Laminates.
Degree: PhD, Engineering Science and Mechanics, 1994, Virginia Tech
URL: http://hdl.handle.net/10919/37216
► A systematic study was conducted to examine the influence of fiber surface treatment and sizing on the formation of fiber-matrix interphase and its effects n…
(more)
▼ A systematic study was conducted to examine the influence of fiber surface treatment and sizing on the formation of fiber-matrix interphase and its effects n the mechanical properties of composite laminates. Three material systems having the same Apollo graphite fibers and HC 9106-3 toughened epoxy matrix, but with different fiber surface treatments and sizings were used in this study. The fibers used in the 810A and 820 A systems received 100% and 200% industry standard surface treatments respectively and were sized with Bisphenol-A unreacted epoxy material. The 810 O system was manufactured with 100% surface treated fibers that were sized with pvp (polyvinylpyrrolidone), a thermoplastic material.
Advisors/Committee Members: Stinchcomb, Wayne W. (committeechair), Kander, Ronald C. (committee member), Kriz, Ronald D. (committee member), Loos, Alfred C. (committee member), Reifsnider, Kenneth L. (committee member).
Subjects/Keywords: graphite fibers; thermoplastics; LD5655.V856 1994.S837
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APA (6th Edition):
Subramanian, S. (1994). Effect of fiber/Matrix Interphase on the Long Term Behavior of Cross-Ply Laminates. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/37216
Chicago Manual of Style (16th Edition):
Subramanian, Suresh. “Effect of fiber/Matrix Interphase on the Long Term Behavior of Cross-Ply Laminates.” 1994. Doctoral Dissertation, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/37216.
MLA Handbook (7th Edition):
Subramanian, Suresh. “Effect of fiber/Matrix Interphase on the Long Term Behavior of Cross-Ply Laminates.” 1994. Web. 17 Apr 2021.
Vancouver:
Subramanian S. Effect of fiber/Matrix Interphase on the Long Term Behavior of Cross-Ply Laminates. [Internet] [Doctoral dissertation]. Virginia Tech; 1994. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/37216.
Council of Science Editors:
Subramanian S. Effect of fiber/Matrix Interphase on the Long Term Behavior of Cross-Ply Laminates. [Doctoral Dissertation]. Virginia Tech; 1994. Available from: http://hdl.handle.net/10919/37216
Virginia Tech
29.
Shih, Po-Jen.
On-Line Consolidation of Thermoplastic Composites.
Degree: PhD, Engineering Science and Mechanics, 1997, Virginia Tech
URL: http://hdl.handle.net/10919/30295
► An on-line consolidation system, which includes a computer-controlled filament winding machine and a consolidation head assembly, has been designed and constructed to fabricate composite parts…
(more)
▼ An on-line consolidation system, which includes a computer-controlled filament winding machine and a consolidation head assembly, has been designed and constructed to fabricate composite parts from thermoplastic towpregs. A statistical approach was used to determine the significant processing parameters and their effect on the mechanical and physical properties of composite cylinders fabricated by on-line consolidation. A central composite experimental design was used to select the processing conditions for manufacturing the composite cylinders. The thickness, density, void content, degree of crystallinity and interlaminar shear strength (ILSS) were measured for each composite cylinder. Micrographs showed that complete intimate contact and uniform fiber-matrix distribution were achieved. The degree of crystallinity of the cylinders was found to be in the range of 25-30%. Under optimum processing conditions, an ILSS of 58 MPa and a void content of <1% were achieved for APC-2 (PEEK/Carbon fiber) composite cylinders.
An in-situ measurement system which uses a slip ring assembly and a computer data acquisition system was developed to obtain temperature data during winding. Composite cylinders were manufactured with eight K-type thermocouples installed in various locations inside the cylinder. The temperature distribution inside the composite cylinder during winding was measured for different processing conditions.
ABAQUS finite element models of the different processes that occur during on-line consolidation were constructed. The first model was used to determine the convective heat transfer coefficient for the hot-air heat source. A convective heat transfer coefficient of 260 w/m2°K was obtained by matching the calculated temperature history to the in-situ measurement data. To predict temperature distribution during winding an ABAQUS winding simulation model was developed . The winding speed was modeled by incrementally moving the convective boundary conditions around the outer surface of the composite cylinder. A towpreg heating model was constructed to predict the temperature distribution on the cross section of the incoming towpreg. For the process-induced thermal stresses analysis, a thermoelastic finite element model was constructed. Using the temperature history obtained from thermal analysis as the initial conditions, the thermal stresses during winding and cooling were investigated.
Advisors/Committee Members: Loos, Alfred C. (committeechair), Gürdal, Zafer (committee member), Cramer, Mark S. (committee member), Heller, Robert A. (committee member), Johnson, Eric R. (committee member).
Subjects/Keywords: none
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APA (6th Edition):
Shih, P. (1997). On-Line Consolidation of Thermoplastic Composites. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/30295
Chicago Manual of Style (16th Edition):
Shih, Po-Jen. “On-Line Consolidation of Thermoplastic Composites.” 1997. Doctoral Dissertation, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/30295.
MLA Handbook (7th Edition):
Shih, Po-Jen. “On-Line Consolidation of Thermoplastic Composites.” 1997. Web. 17 Apr 2021.
Vancouver:
Shih P. On-Line Consolidation of Thermoplastic Composites. [Internet] [Doctoral dissertation]. Virginia Tech; 1997. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/30295.
Council of Science Editors:
Shih P. On-Line Consolidation of Thermoplastic Composites. [Doctoral Dissertation]. Virginia Tech; 1997. Available from: http://hdl.handle.net/10919/30295
Virginia Tech
30.
Bullions, Todd Aaron.
Manufacture of and Environmental Effects on Carbon Fiber-Reinforced PhenylEthynyl-Terminated Poly(EtherImide).
Degree: PhD, Materials Science and Engineering, 2000, Virginia Tech
URL: http://hdl.handle.net/10919/28962
► The initial objective of this research project was to determine the feasibility of manufacturing carbon fiber-reinforced (CFR) composites with a matrix consisting of a phenylethynyl-terminated…
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▼ The initial objective of this research project was to determine the feasibility of manufacturing carbon fiber-reinforced (CFR) composites with a matrix consisting of a phenylethynyl-terminated version of a thermoplastic poly(etherimide) termed PETU. Successful composite manufacture with 3,000 g/mol (3k) PETU led to a survey of CFR 3kPETU mechanical properties for comparison with other high-performance composites. Encouraging results led to a study of moisture sorption effects on CFR 3kPETU properties. The success of these initial studies spawned the large scale production of 2,500 g/mol (2.5k) PETU.
Thermal characterization of neat and CFR 2.5kPETU via differential scanning calorimetry, dynamic mechanical thermal analysis, and parallel plate rheometry resulted in an understanding of the influence of cure time and temperature on reaction progress via both reaction kinetics and monitoring of the glass transition temperature. From the rheological characterization, a two-stage, dual-Arrhenius model was developed to successfully model isothermal complex viscosity over the range of processing temperatures.
Neat 2.5kPETU and CFR 2.5kPETU specimens were exposed separately to elevated temperature environments of different moisture and different oxygen concentrations to evaluate the effects of moisture absorption, moisture desorption, and thermal oxidation on material properties. Moisture absorption took place in a 90 °
C / 85% relative humidity environment followed by moisture desorption in a 90 °
C / 10% relative humidity environment. Thermal-oxidative aging for up to 5000 hours took place at 204 204 °
C in environments of four different oxygen partial pressures: 0.0 kPa, 2.84 kPa, 20.2 kPa, and 40.4 kPa. Following exposure to the different aging environments, the specimens were tested for retention of mechanical properties. In addition, moisture sorption properties were measured.
Results from the moisture sorption studies on CFR 3kPETU and CFR 2.5kPETU suggest that fully cured composites will withstand moisture absorption and desorption with negligible effects on mechanical properties, whereas, lack of full cure allows moisture sorption to permanently damage the composites. Despite a lack of mass loss or visual evidence of degradation following thermal-oxidative aging, a decline in mechanical properties was observed with the reduction becoming greater with longer aging times and higher oxygen partial pressures.
Advisors/Committee Members: Loos, Alfred C. (committeechair), Dillard, David A. (committee member), Baird, Donald G. (committee member), Kander, Ronald G. (committee member), McGrath, James E. (committee member).
Subjects/Keywords: glass transition temperature; rheology; composite; dry powder prepregging; phenylethynyl-terminated poly(etherimide); moisture; thermal-oxidative aging; cure kinetics
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Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Bullions, T. A. (2000). Manufacture of and Environmental Effects on Carbon Fiber-Reinforced PhenylEthynyl-Terminated Poly(EtherImide). (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/28962
Chicago Manual of Style (16th Edition):
Bullions, Todd Aaron. “Manufacture of and Environmental Effects on Carbon Fiber-Reinforced PhenylEthynyl-Terminated Poly(EtherImide).” 2000. Doctoral Dissertation, Virginia Tech. Accessed April 17, 2021.
http://hdl.handle.net/10919/28962.
MLA Handbook (7th Edition):
Bullions, Todd Aaron. “Manufacture of and Environmental Effects on Carbon Fiber-Reinforced PhenylEthynyl-Terminated Poly(EtherImide).” 2000. Web. 17 Apr 2021.
Vancouver:
Bullions TA. Manufacture of and Environmental Effects on Carbon Fiber-Reinforced PhenylEthynyl-Terminated Poly(EtherImide). [Internet] [Doctoral dissertation]. Virginia Tech; 2000. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10919/28962.
Council of Science Editors:
Bullions TA. Manufacture of and Environmental Effects on Carbon Fiber-Reinforced PhenylEthynyl-Terminated Poly(EtherImide). [Doctoral Dissertation]. Virginia Tech; 2000. Available from: http://hdl.handle.net/10919/28962
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