Mazahir, Syed Makhmoor.
Improvement in Orientation Predictions of High-Aspect Ratio Particles in Injection Mold Filling Simulations.
Degree: PhD, Chemical Engineering, 2013, Virginia Tech
Glass fiber based polymer composites based injection molded parts provide a light-weight high-strength alternative for use in automobile applications. These composites have enhanced mechanical properties compared to those of pure polymers, if the fibers are oriented in the right direction. One of the major challenges in processing of these composites is to control the fiber orientation in the final product. The evolution of short glass fiber orientation in a center-gated disk was experimentally determined along the radial direction at three different heights representative of the shell, transition and core layers, respectively. Orientation data along the shell and transition layers in the lubrication region show shear flow effects, which tends to align the fibers along the flow direction. In the core layer, where the extension in the "-direction dominates, fibers tend to get aligned along the "-direction. In the frontal flow region orientation in the flow direction drops in all three layers due to fountain flow effects. Fiber orientation predictions in coupled and decoupled transient simulations using the Folgar-Tucker model, and the two slow versions of the Folgar-Tucker model, namely the slip Folgar-Tucker model and the reduced strain closure (RSC) model were compared with the experimental data. Measured inlet orientation was used in all simulations and model parameters were determined by fitting model predictions to rheological data under startup of shear. Pseudo-concentration method was implemented for the modeling of the advancing front and fountain flow effects in the region near the front. Discontinuous Galerkin finite element method and a third order Runge-Kutta total variance diminishing time integration scheme were implemented for the solution of the orientation and transport equations. In the lubrication region of the shell layer, all three orientation models provided a good match with the experimental data. In the frontal region, fountain flow simulations showed characteristic features seen in r- and z-profiles of orientation, although the experimental data showed these features at a relatively larger distance behind the front while the simulations predicted these effects only upto a small distance behind the front. On the other hand, orientation predictions with the Hele-Shaw flow approximation showed significant over-predictions in the frontal region. With model parameters determined from fitting to rheological data, coupling did not show any significant improvements. However, with the use of a smaller value of the fiber interaction parameter, coupling showed significant improvement in orientation predictions in all three layers in the frontal region. The simulation scheme was extended to long fiber systems by comparing available long fiber orientation data in a center-gated disk with model predictions using the Bead-Rod model which considers fiber bending, a property exhibited by long semi-flexible fibers. The Bead-Rod model showed improvements over rigid fiber models in the…
Advisors/Committee Members: Baird, Donald G. (committeechair), Wapperom, Peter (committeechair), Martin, Stephen Michael (committee member), Joseph, Eugene Gregory (committee member).
Subjects/Keywords: Fiber Orientation; Center-Gated Disk; Injection Molding; Fountain Flow; Advancing Front; Radial Evolution; Coupled Flow; Finite Element Analysis
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APA (6th Edition):
Mazahir, S. M. (2013). Improvement in Orientation Predictions of High-Aspect Ratio Particles in Injection Mold Filling Simulations. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/50654
Chicago Manual of Style (16th Edition):
Mazahir, Syed Makhmoor. “Improvement in Orientation Predictions of High-Aspect Ratio Particles in Injection Mold Filling Simulations.” 2013. Doctoral Dissertation, Virginia Tech. Accessed December 16, 2019.
MLA Handbook (7th Edition):
Mazahir, Syed Makhmoor. “Improvement in Orientation Predictions of High-Aspect Ratio Particles in Injection Mold Filling Simulations.” 2013. Web. 16 Dec 2019.
Mazahir SM. Improvement in Orientation Predictions of High-Aspect Ratio Particles in Injection Mold Filling Simulations. [Internet] [Doctoral dissertation]. Virginia Tech; 2013. [cited 2019 Dec 16].
Available from: http://hdl.handle.net/10919/50654.
Council of Science Editors:
Mazahir SM. Improvement in Orientation Predictions of High-Aspect Ratio Particles in Injection Mold Filling Simulations. [Doctoral Dissertation]. Virginia Tech; 2013. Available from: http://hdl.handle.net/10919/50654