Experimental and analytical investigation of failure behavior in satin-weave composites and uni-weave/satin-weave hybrid composites

The objectives of this dissertation research are to identify the failure modes in satin-weave composites and uni-weave/satin weave hybrid composites under different mechanical load and environmental conditions and develop a better understanding of the factors that affect failure behavior.; To reach these aims, various experimental techniques have been utilized to characterize damage initiation and development under tension and compression. A three-dimensional Finite Element Analysis was used to understand the observed damage behavior. The effects of hygrothermal aging, free surfaces and hybridization on failure mechanisms were also investigated.; Experimental observations indicate that the damage initiation and development under uniaxial tension are different between satin-weave composites and uni-weave/satin-weave hybrid composites. Compressive failure strains and failure modes are affected by the lay-up of the composite laminates. Fiber bundle kinking induced by intra-ply delamination was the dominant failure modes in the satin-weave ([S] ₁₂) and the axial hybrid composites ([(0/S)₃/0/S/0/(S/0) ₃]). However, the failure mode is fiber crushing for the transverse hybrid composites ([(90/S)₃/90/S/90/(S/90)₃]). The deterioration of the interfacial adhesion as a result of hygrothermal aging is the most important factor contributing to the degradation of the mechanical performance of BMI composites, especially for compressive strength.; Finite element results successfully explain some experimental observations. The stress distributions in the surface layer were found to be independent of the thickness of the laminates for the symmetrically stacked laminates. However, for simply stacked laminates, the response of the surface layers is quite sensitive to the thickness except for fairly thick laminate. The hybridization effects on the stress distribution are also largely dependent on the degree of waviness and the stacking configurations.