Micromechanical modelling of nonlinear deformation and damage processes in disordered composites

This study deals with the investigation of the nonlinear deformation and damage processes in the matrix of the unidirectional fiber-reinforced composite with fibers disordered in transversal plane at combined transversal and longitudinal shear loading. The nonlinear boundary-value problem for the composite fragments is considered to calculate the stress and strain fields in matrix and fibers of the composite. The macrostress and macrostrain are calculated by averaging these fields upon a sample of the composite fragments. The matrix constitutive equations include formulas of deformation theory of plasticity and stiffness reduction relation a for zones where a strength criterion is broken. Fibers were elastic and nonfractured. The macrostress-macrostrain curves for some epoxy composite with fibers from glass, carbon, boron and kevlar were constructed. The comparison with the results for the composite model with the fiber periodic arrangement was performed.