Effect of Large Holes and Platelet Width on the Openhole Tension Performance of Prepreg Platelet Molded Composites

Gabriel Gutierrez, Purdue University

Abstract

Carbon-fiber reinforced polymers (CFRPs) are often used in the aerospace and automotive industries for their high strength-to-weight ratios and corrosion resistance. A new class of composites – known as Prepreg Platelet Molded Composites (PPMCs) – offers further advantageous such as high forming capabilities with modest compromises in strength and stiffness. One such property of PPMCs that have garnered interest over the years is their apparent insensitivity to notches. Previous studies have researched the effect of specimen size and platelet length on its effect on the open-hole performance of PPMCs. Research however has focused on thinner samples with smaller hole sizes and neglected thicker samples with larger holes. Additionally, while platelet sizes have been investigated for unnotched samples, platelet width on notched samples is less clear from the literature. The present thesis offers some investigations to aid in filling this knowledge gap.The objective of this work is to study two parameters that could influence the performance of PPMCs under open-hole tension. First, thick (7.6 mm) specimens are subjected to large hole sizes (up to 19.08 mm) to investigate their behavior in comparison to the smaller sample sizes previously investigated in the literature. Through-thickness DIC measurements are taken to investigate strain gradients in these thicker specimens. Second, various platelet widths are tested to research their influence on notch insensitivity of open-hole tensile PPMC specimens. Lastly, a finite element based continuum damage mechanics model is implemented to predict macro-level structural properties using only material properties of the parent prepreg. It is found that large holes in thick samples increase notch sensitivity compared to other samples of similar diameter-to-width ratios. Narrower platelets were found to produce higher unnotched strengths, while wider platelets offered more notch insensitivity. Lastly, the finite element model developed was found to qualitatively replicate features and failure modes that are exhibited by PPMCs, though strength predictions became inaccurate at larger specimen sizes. Recommendations are made for future work on the basis of these findings.

Degree

M.Sc.

Advisors

Pipes, Purdue University.

Subject Area

Mechanics|Industrial engineering|Marketing|Materials science|Statistics

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