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You searched for subject:(fiber misalignment). Showing records 1 – 2 of 2 total matches.

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1. Stangler, Luke. The Effects of Carbon Fiber Misalignment on Composite Material Strength.

Degree: MS, Mechanical Engineering, 2016, South Dakota State University

Nondestructive Evaluation (NDE) is an effective way for determining material properties. More specifically, ultrasonic waves along with visual measurements from a microscope can be used to systematically determine the elastic modulus of single ply composites that are subject to an altered manufacturing process. In this approach, the magnitude of specific ultrasonic wave velocities is applied through Chirstoffel's equations to determine the necessary five elastic constants that describe the elastic modulus of transversely isotropic composites. On the other hand, fiber misalignment measurements are taken through via digital microscopy to satisfy a statistical approach for the determination of the same elastic modulus. The Paper Physics Approach (PPA) and Laminate Analogy Approach (LAA) are utilized to predict the elastic modulus of unidirectional carbon fiber samples. A two parameter Weibull distribution is expected to satisfy the probability density of the fiber length and fiber orientation variation which will then be implemented into the Halpin-Tsai equations that will determine the elastic modulus. In terms of results, the mean fiber length from the visual approach is approximately 250 μm and the mean fiber misalignment is just over 3°. The elastic constants range from 7 GPa to 9 GPa depending on the approach. Destructive mechanical testing led to an average elastic modulus value of 8.49 GPa. Advisors/Committee Members: Zhong Hu.

Subjects/Keywords: carbon; fiber; laminate; misalignment; modulus; unidirectional; Mechanical Engineering

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Stangler, L. (2016). The Effects of Carbon Fiber Misalignment on Composite Material Strength. (Masters Thesis). South Dakota State University. Retrieved from http://openprairie.sdstate.edu/etd/678

Chicago Manual of Style (16th Edition):

Stangler, Luke. “The Effects of Carbon Fiber Misalignment on Composite Material Strength.” 2016. Masters Thesis, South Dakota State University. Accessed November 19, 2019. http://openprairie.sdstate.edu/etd/678.

MLA Handbook (7th Edition):

Stangler, Luke. “The Effects of Carbon Fiber Misalignment on Composite Material Strength.” 2016. Web. 19 Nov 2019.

Vancouver:

Stangler L. The Effects of Carbon Fiber Misalignment on Composite Material Strength. [Internet] [Masters thesis]. South Dakota State University; 2016. [cited 2019 Nov 19]. Available from: http://openprairie.sdstate.edu/etd/678.

Council of Science Editors:

Stangler L. The Effects of Carbon Fiber Misalignment on Composite Material Strength. [Masters Thesis]. South Dakota State University; 2016. Available from: http://openprairie.sdstate.edu/etd/678


Clemson University

2. Thompson, Ronald. Compressive Strength of Continuous Fiber Unidirectional Composites.

Degree: PhD, Mechanical Engineering, 2012, Clemson University

Dow and Rosen's work in 1965 formed an intellectual framework for compressive strength of unidirectional composites. Compressive strength was explained in terms of micro-buckling, in which filaments are beams on an elastic foundation. They made simplifying assumptions, with a two dimensional idealization and linearized material properties. This study builds on their model, recognizing that the shear mode of instability drives unidirectional compressive strength. As a necessary corollary, the predictive methods developed in this study emphasize correct representation of composite shear stiffness. Non-linear effects related to matrix material properties, fiber misalignment, three dimensional representation, and thermal prestrains are taken into account. Four work streams comprise this study: first, development of a closed form analytical model; second, empirical methods development and model validation; third, creation and validation of a unit cell finite element model; and fourth, a patent application that leverages knowledge gained from the first three work streams. The analytical model characterizes the non-linearity of the matrix both with respect to shear and compressive loading. This improvement on existing analyses clearly shows why fiber modulus affects composite shear instability. Accounting for fiber misalignment in the model and experimental characterization of the fiber misalignment continuum are important contributions of this study. A simple method of compressive strength measurement of a small diameter monofilament glass-resin composite is developed. Sample definition and preparation are original, and necessary technologies are easily assessable to other researchers in this field. This study shows that glass fiber composites have the potential for high compressive strength. This potential is reached with excellent fiber alignment and suitable matrix characteristics, and results are consistent with model predictions. The unit cell three dimensional finite element model introduces a boundary condition that only allows compressive and shear deformation, thus recognizing the actual deformation mechanism of a compressed unidirectional composite. A new approach for representing the resin matrix is employed, giving improved correlation to empirical measurements noted in the literature. A method of accounting for realistic composite imperfections is introduced. The patent application work was fed by results from the first three areas. A new engineering structure is created in which buckling is beneficial. Post buckled behavior favorably affects other structural components in an overload situation. The first three work streams form a coherent unit and are mutually supportive. The analytical model predictions are corroborated by the experimental measurements. Finite element model predictions are consistent with the analytical model predictions. Advisors/Committee Members: Joseph, Paul, Blouin , Vincent, Biggers , Sherrill, Gruijicic , Mica, Rhyne , Timothy.

Subjects/Keywords: composite; compressive strength; fiber misalignment; finite element analysis; matrix nonlinearity; microbuckling; Mechanical Engineering

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Thompson, R. (2012). Compressive Strength of Continuous Fiber Unidirectional Composites. (Doctoral Dissertation). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_dissertations/953

Chicago Manual of Style (16th Edition):

Thompson, Ronald. “Compressive Strength of Continuous Fiber Unidirectional Composites.” 2012. Doctoral Dissertation, Clemson University. Accessed November 19, 2019. https://tigerprints.clemson.edu/all_dissertations/953.

MLA Handbook (7th Edition):

Thompson, Ronald. “Compressive Strength of Continuous Fiber Unidirectional Composites.” 2012. Web. 19 Nov 2019.

Vancouver:

Thompson R. Compressive Strength of Continuous Fiber Unidirectional Composites. [Internet] [Doctoral dissertation]. Clemson University; 2012. [cited 2019 Nov 19]. Available from: https://tigerprints.clemson.edu/all_dissertations/953.

Council of Science Editors:

Thompson R. Compressive Strength of Continuous Fiber Unidirectional Composites. [Doctoral Dissertation]. Clemson University; 2012. Available from: https://tigerprints.clemson.edu/all_dissertations/953

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