Date of Award

Spring 2021

Project Type

Dissertation

Program or Major

Mechanical Engineering

Degree Name

Doctor of Philosophy

First Advisor

Igor I Tsukrov

Second Advisor

Todd Gross

Third Advisor

Borys Drach

Abstract

3D woven carbon/epoxy composites are high-performance materials with superior thermo-mechanical and physical properties making them an integral part of the aerospace, energy and automotive industries. However, under certain manufacturing conditions, these composites may accumulate severe intrinsic manufacturing-induced residual stresses which can even lead to microcracking. The complex reinforcement architecture makes analytical, numerical and experimental analysis of these composites challenging. This research has been focused on micromechanical analysis, computational modeling, and experimental characterization of 3D woven carbon/epoxy composites aiming to evaluate the manufacturing-induced residual stresses and enable mitigation of their negative impact on the resulting performance. A procedure to develop high-fidelity meso-scale finite element models with as-woven representation of the composite reinforcement informed by the μCT scanning was proposed. A set of meso-scale models for different reinforcement architectures was produced and utilized to predict the accumulation of intrinsic manufacturing-induced residual stresses in these composites. The models were correlated to the blind hole drilling experiments and used for interpretation of the experimental results providing full-field spatial distribution of the residual stresses accumulated in the composite specimens. A new simplified approach to account for nonlinear effects in the material due to severe residual stresses using linearly-elastic models was proposed. A set of parametric numerical studies was performed to improve correlation of the models with the experimental measurements. The developed meso-scale models were used to predict effective coefficients of thermal expansion for the composites with temperature-dependent properties of the constituents. Methods presented in this work provide valuable tools for the field of computational and experimental mechanics of textile composite materials.

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