Effect of Material Anisotropy and Curing Stresses on Interface Delamination Propagation Characteristics in Multiply Laminated FRP Composites

The present study encompasses the thermoelastic effect of material anisotropy and curing stresses on interlaminar embedded elliptical delamination fracture characteristics in multiply laminated fiber-reinforced polymeric (FRP) composites. Two sets of full three-dimensional finite element analyses have been performed to calculate the displacements and interlaminar stresses along the delaminated interface 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. It is shown that the individual modes of energy release rates vary along the delamination front depending on the ply sequence, orientation, and thermoelastic material anisotropy of the constituting laminae. This causes the anisotropic and non-self similar delamination propagation along the interface. The asymmetric and nonuniform variations in the nature of energy release rate plots obtained in a thermomechanical loading environment are significant when curing stress effects are included in the numerical analysis and hence should be taken into account in the designs of laminated FRP composite structures.