Multi scale modeling and characterization of inelastic deformation mechanisms in continuous fiber and 2D woven fabric reinforced metal matrix composites

Continuous unidirectional ceramic fiber and woven fabric reinforced metal matrix composites (MMCs) have potential to obtain very high specific strengths and stiffnesses, but use in structural applications has thus far been limited by their inherently low ductility, particularly in tensile loading conditions. In this work, a multi-scale micromechanics based finite element framework is used to predict, and understand the effect of microstructure on the tensile deformation behavior, including progressive damage and failure, of ceramic fiber and fabric reinforced MMCs. A hierarchal approach is implemented in which a micro-scale model is used to determine the transversely isotropic elasto-plastic mechanical behavior of unidirectional fiber reinforced MMC based on the properties of an aluminum alloy matrix, individual ceramic fibers, and the fiber–matrix interface. The validated transversely isotropic constitutive behavior is then input into a unit cell model for a woven fabric MMC consisting of unidirectional MMC tows in an aluminum matrix. Parallel experimental tensile testing and characterization of fracture mechanisms are used to validate our model for unidirectional and 2D weave fabric MMC. Cohesive zones are used to model the interfacial properties at both scales and we are able to quantify the contribution of various deformation and damage mechanisms such as ductile matrix failure, interfacial decohesion, transverse plasticity, and axial fiber fracture to the overall mechanical response of the MMC. It was found that interfacial debonding contributes significantly to the inelastic response of unidirectional and woven fabric MMC and that experimental data are relatively well reproduced by a model that assumes a weak interfacial debonding cohesive law (maximum allowable interface stresses on the order of 100MPa and total work of decohesion=75J/m2).