DAMAGE EVOLUTION MODELING IN ORTHOTROPIC LAMINATED COMPOSITES

Composites have inherent scatter in elastic and strength properties. A probabilistic model utilizing random material characteristics to predict damage evolution in orthotropic laminated composites is presented in this paper. The proposed model is based on the division of laminated composites into a statistically large number of mesoelements (mesovolumes). The mesovolume is assumed to be large enough to be structurally homogeneous, and at the same time it has to be comparatively small to satisfy the condition of stochastic homogeneity of stress and strain fields. Three modes of mesovolume failure, i.e., fibre breakage and matrix failure in the transverse direction as well as matrix shear cracking, are taken into account. Damage formation in a ply and in a laminate as a whole for a given plane stress state is calculated from the probabilities of mesovolume failure. These probabilities are directly utilized in reducing ply material constants. A numerical algorithm for damage accumulation and deformation history predictions for orthotropic laminated composites are developed. The behavior of a laminated orthotropic composite is presented as an illustrative example. Analysis of angle-ply Kevlar/epoxy laminates subjected to tension, compression, and shear loading is performed. The effect of scatters in elastic and strength characteristics on damage evolution is shown.