Progressive failure analysis of laminated composite beams

A progressive failure model for laminated composite beams is formulated using a beam finite element with layer-wise constant shear (BLCS), which permits accurate computation of stresses on each layer. This is the first study to incorporate the stress-prediction accuracy of a layer-wise element for failure prediction of laminates under bending loads. In the present formulation, based on material degradation factors and existing failure criteria, a linear elastic behavior is assumed, and a damaged layer in an element is substituted by a degraded homogeneous layer. Maximum Stress and Tsai-Wu failure criteria are used to assess failure at the Gauss points. The effect of damage accumulation is accounted for by degrading the stiffness properties of failed element-layers in the equilibrium iterations. After equilibrium is satisfied, the load is increased by a constant percentage of first-play-failure load in a load-controlled failure prediction. A displacement-controlled scheme is also implemented. The predictions of the model correlate well with experimental results for two distinct laminated composite beams: graphite-epoxy and glulam reinforced with GFRP. The study provides guidelines, through parametric studies, for the appropriate selection of material-degradation factors, load increments, and finite element mesh.