Influence of Ply Sequence and Thermoelastic Stress Field on Asymmetric Delamination Growth Behavior Emanating From Elliptical Holes in Laminated FRP Composites

The present study encompasses the influence of ply sequence and thermoelastic stress field on asymmetric delamination growth behavior emanating from elliptical holes in laminated fiber reinforced polymeric composites. Results, emphasizing the effect of thermal residual stresses on delamination growth behavior of the composite laminates subjected to two different loading conditions, i.e., in-plane tensile and compressive loadings, are presented. Two sets of full three-dimensional finite element analyses have been performed to calculate the displacements and interlaminar stresses along the delaminated interfaces responsible for the delamination onset and propagation. Modified crack closure integral methods based on the concepts of linear elastic fracture mechanics have been followed to evaluate the individual modes of strain energy release rates along the delamination front. In each case, the delamination is embedded at a different depth along the thickness direction of the laminates. It is observed that the fiber orientation of the plies bounding the delamination front significantly influences the distribution of the local strain energy release rate. Also, the residual thermal stresses have a detrimental effect on the laminates subjected to compressive loading and more so in the case of laminates with delaminations existing closer to the top and bottom surfaces of the laminate.