Elastoplastic Micromechanical Damage Mechanics for Composites with Progressive Partial Fiber Debonding and Thermal Residual Stress

By incorporating interfacial damage and thermal residual stress, a novel elastoplastic damage model is proposed to predict the overall transverse mechanical behavior of fiber-reinforced ductile matrix composites within the framework of micromechanics. Based on the concept of equivalent fiber, and taking the debonding angle into consideration, partially debonded isotropic fibers are replaced by equivalent orthotropic yet perfectly bonded elastic fibers. Up to three interfacial damage modes (no debonding, partial debonding and perfect debonding) are considered. The Weibull’s probabilistic function is employed to describe the varying probability of progressive partial fiber debonding. The effective elastic moduli of four-phase composites, composed of a ductile matrix and randomly located yet unidirectionally aligned fibers (undamaged/damaged) are derived by a micromechanical formulation. Thermal residual stress is taken into account through the concept of thermal eigenstrain to study the effect of the manufacturing process-induced residual stress. Further, explicit exact formulation on the exterior point Eshelby tensor for elliptical fiber is utilized to investigate the effect on the inelastic mechanical responses of the composites due to the aspect ratio of elliptical fiber.