Date of Award

Spring 5-1-2020

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

Advisor

Senthil S. Vel

Second Committee Member

Roberto A. Lopez-Anido

Third Committee Member

Zhihe Jin

Abstract

Composite materials are widely used in aerospace, automotive and wind power industries due to their high strength-to-weight and stiffness-to-weight ratios and their improved mechanical properties compared to metals. The damage resistance of composite materials due to low velocity impact depends on fiber breakage, matrix cracking and delamination between the interfaces. In this research, a numerical investigation of low velocity impact response of a multidirectional symmetric carbon-epoxy composite laminate is carried out and presented. Two different finite element models are developed for composite laminates made of non-crimp fabric to investigate their behavior under different levels of impact energy. In the first approach, a finite element homogeneous ply model is generated wherein the heterogeneous plies are replaced by equivalent homogeneous anisotropic plies. In the second approach, a finite element mesoscale model that captures the individual constituents of the composite (i.e., the tows and matrix) has been developed. Different failure criteria have been presented in the literature to predict the damage modes of the composites during and after impact events. The 3D Hashin failure criteria is implemented to predict the intralaminar failure and the surface-based cohesive behavior is implemented to capture the delamination between the plies. Following the low velocity impact investigation, the finite element models are subjected to axial compression to investigate the compressive residual strength after impact, which is a measure of damage tolerance. The numerical predictions, the low velocity impact response as well as the compressive residual strength after impact, are validated with experimental data. The homogeneous ply laminate impacted up to 50 J is seen to be capable of predicting the impact response as well as the compressive residual strength after impact.

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