Effective elastoplastic damage mechanics for fiber-reinforced composites with evolutionary complete fiber debonding ABSTRACT: A micromechanical damage mechanics framework is proposed to predict the overall elastoplastic behavior and interfacial damage evolution of fiberreinforced ductile composites. Progressively debonded fibers are replaced by equivalent voids. The effective elastic moduli of three-phase composites, composed of a ductile matrix, randomly located yet unidirectionally aligned circular fibers, and voids, are derived by using a rigorous micromechanical formulation. In order to characterize the homogenized elastoplastic behavior, an effective yield criterion is derived based on the ensemble area averaging process and the first-order effects of eigenstrains. The resulting effective yield criterion, together with the overall associative plastic flow rule and the hardening law, constitutes the analytical framework for the estimation of effective elastoplastic damage responses of ductile composites containing both perfectly bonded and completely debonded fibers. An evolutionary interfacial fiber debonding process, governed by the internal stresses of fibers and the interfacial strength, is incorporated into the proposed framework. The Weibull's function is employed to describe the varying probability of fiber debonding. Further, comparison between the predictions and available experimental data are presented to illustrate the potential of the proposed methodology.

A micromechanical multi-level elastoplastic evolutionary damage framework is proposed to predict the overall mechanical behavior and interfacial damage evolutions of elliptical fiber-reinforced ductile composites. Progressively debonded fibers are replaced by equivalent microvoids. The effective elastic moduli of three phase composites, composed of a ductile matrix, randomly located yet monotonically aligned elliptical fibers and elliptical microvoids, are derived by using a micromechanical formulation. In order to characterize the homogenized elastoplastic behavior, an effective yield criterion is derived based on the ensemble-area averaging process and the first-order effects of eigenstrains. The resulting effective yield criterion, together with the overall associative plastic flow rule and the hardening law, constitutes the analytical framework for the estimation of effective elastoplastic damage responses of ductile composites containing both perfectly bonded and completely debonded fibers. An evolutionary interfacial fiber debonding process, governed by the internal stresses of fibers and the interfacial strength, is incorporated into the proposed work. The Weibull's probabilistic distribution is employed to describe the varying probability of fiber debonding. Further, systematic numerical simulations are presented to illustrate the potential of the proposed methodology.

A micromechanical two-level elastoplastic evolutionary damage model is proposed to predict the overall transverse mechanical behavior and interfacial damage evolution of fiber-reinforced ductile matrix composites. Progressive partially debonded cylindrical isotropic long fibers are replaced by equivalent orthotropic yet perfectly bonded elastic cylindrical inclusions. Up to three interfacial fiber debonding damage modes in two dimensions are considered. The effective elastic moduli of five-phase composites, composed of a ductile matrix, randomly located yet unidirectionally aligned cylindrical fibers, and equivalent (damaged) cylindrical fibers, are derived by using a micromechanical formulation. In order to characterize the overall transverse elastoplastic damage behavior, an effective yield criterion is derived based on the statistical ensemble-area averaging process and the first-order effects of eigenstrains upon overall yielding. The proposed effective yield criterion, together with the overall plastic flow rule and the hardening law, constitute the 3-D analytical homogenization framework for the estimation of effective elastoplastic damage responses of metal matrix composites containing both perfectly bonded and partially debonded aligned cylindrical fibers randomly located in the matrix. Further, the Weibull's probabilistic function is employed to describe the varying probability of progressive partial cylindrical fiber debonding. The proposed micromechanical elastoplastic damage formulation is applied to the transverse uniaxial and varied stress ratios of transverse biaxial tensile loading to predict the various stress—strain responses under the plane-strain condition. Efficient computational algorithms are also presented to implement the proposed elastoplastic damage model. Finally, comparison between the present predictions and available experimental data and other simulations are performed to illustrate the potential of the proposed framework.

A micromechanical multi-level elastoplastic evolutionary damage framework is proposed to predict the overall transverse mechanical behavior and damage evolutions of cylindrical fiber-reinforced ductile composites. Progressively cracked fibers are modeled using the double-inclusion theory. The effective elastic moduli of three-phase composites, consisting of a matrix, randomly located yet monotonically aligned cylindrical uncracked fibers and cracked fibers, are derived by using a micromechanical formulation. In order to characterize the homogenized elastoplastic behavior, a micromechanical effective yield criterion is derived based on the ensemble-area averaging process and the first-order effects of eigenstrains. The resulting effective yield criterion, together with the overall associative plastic flow rule and the hardening law, constitutes the analytical framework for the estimation of effective transverse elastoplastic-damage responses of ductile composites containing both uncracked and cracked fibers. An evolutionary fiber cracking process, governed by the internal stresses and the fracture strength of fibers, is incorporated into the proposed work. The Weibull's probabilistic distribution is employed to describe the varying probability of fiber cracking. Further, systematic numerical simulations are presented to illustrate the potential of the proposed methodology.