Elastic behaviour and damage of three-dimensional woven fabric composites

The goal of this research was to investigate the elastic properties and damage behaviour of three-dimensional woven fabric composites. Transformed stiffness and compliance matrices have been obtained in closed-form expressions for orthotropic materials. We introduced three orthotropic constants which enable the transformation to be greatly simplified. A deformation model has been established based on the force equilibrium of a slice of a fabric. Two three-dimensional woven fabrics with different weaving structures and yarn cross-sections were examined. Experiments have been conducted for the three-axis fabrics. Comparisons have been made between experimental and analytical results. The damage mechanisms due to tensile and flexural loads have been observed. in both loading cases, defects around the through-the-thickness yarns have been found to be critical in crack initiation. Being the crack initiators, these defects can be detrimental to the in-plane properties.