Micromechanical fracture modeling of unidirectional composite material under transverse loading

A micromechanical model is presented to analyze the fracture response of unidirectional composite materials considering the nonlinear behavior of matrix material under loading more than the yield strength as well as the fiber-matrix debonding and matrix cracking. The composite microstructure is characterized with repeating unit cell with regular or random fiber-packing patterns. The micromechanical model is employed for composite material with aluminum matrix and carbon fibers. The high rigidity fibers are modeled as linear isotropic elastic material, while matrix material is characterized with elastic-plastic model. The damage initiation stage in matrix material is described by principal strain criterion accompanied with damage evolution considering stiffness degradation up to crack formation. The bonding between fiber and matrix is modeled using cohesive model, in which damage initiation criterion depends on the normal and shear strength of the cohesive zone. The micromechanical model is employed to study the effects of fiber distribution, fiber volume fraction, fiber-matrix bonding strength on the crack propagation through the microstructure as well as the stress-stain graph up to the fracture of microstructures.