Inelastic microbuckling of composites by wave-buckling analogy

Microbuckling in fiber-reinforced elastic composite materials, associated with the composite compressive strength, has been extensively studied over the years. A two-dimensional problem of a periodically layered bi-material, in which the stiff and soft layers represent the fibers and matrix, respectively, has been frequently used to model the composite. The wave-buckling analogy is used for the analysis of inelastic bifurcation microbuckling in layered composites. To this end, the instantaneous stiffness tensor of the inelastic layer is used in the bifurcation buckling analysis. Inelastic material behavior reveals softening, which can be viewed as the reduction of the material mechanical properties. Plasticity is observed to decrease the volume fraction at which the transition occurs from short-wave buckling to long-wave buckling. A solution was obtained by using the analogy between the buckling and wave propagation problems, in conjunction with an incremental approach, while adopting an elastic-viscoplastic constitutive law indicating plasticity reduction of all the involved moduli.