Effective elastoplastic-damage model for fiber-reinforced metal matrix composites with evolutionary fibers debonding.

摘要

A rigorous micromechanical homogenization framework is proposed to predict the effective elastoplastic-damage responses of continuous fiber-reinforced ductile metal matrix composites with unidirectionally aligned and randomly distributed circular and elliptical fibers under transverse loadings. To estimate the overall elastoplastic-damage behavior, an effective yield criterion is micromechanically derived based on the ensemble-area averaging procedure and the first-order effects of eigenstrains due to cylindrical inclusions. The effects of random dispersion of elastic inclusions are considered through the ensemble averaging process. The proposed overall yield criterion, in conjunction with the overall associative plastic flow rule and the hardening law, provide the analytical foundation for the estimation of effective elastoplastic-damage responses. An evolutionary interfacial debonding model is subsequently employed in accordance with the Weibull's probability function to characterize the varying probability of fiber debonding. Progressively debonded circular fibers are regarded as voids in Chapter 2. In Chapter 3, various damage modes of partial circular fiber debonding are considered, and partially debonded elastic circular fibers are replaced by equivalent orthotropic inclusions for the homogenization.; Chapter 4 is devoted to propose a new damage parameter to simulate the evolutionary debonding angle. Three types of debonding modes are considered. For each type of debonded circular fibers, the elastic equivalency is constructed in terms of the equivalent orthotropic stiffness tensor. The proposed constitutive framework is suitable for accommodating general two-dimensional loading conditions.; In Chapter 5, the proposed rigorous micromechanical framework is applied to investigate the elastoplastic-damage stress-strain responses of fiber-reinforced ductile metal matrix composites with elliptical inclusions. To simulate the debonding evolution, the volume fraction of debonded fibers is expressed in terms of the Weibull's statistical functions. Progressively debonded fibers are replaced by equivalent voids. The effects of interfacial debonding and the aspect ratio of the elliptical fibers on the overall stress-strain relations of the composites are studied and illustrated via numerical examples as well.; Finally, Chapter 6 concludes the current research to date and discusses the planned future research topics.