Prediction of induced delamination development in [θ/90]_s composite laminates using a computational analytical approach

Most of the conducted studies on investigating the effect of induced delamination formation have been devoted to the cross-ply laminates under uniaxial loading. In this paper by implementing an energy-based theory, the induced delamination onset due to matrix cracking has been studied in [θ/90]_s composite laminates subjected to general in-plane remote stresses. For this purpose, the formation of induced delamination has been analyzed based on generalized plane strain assumptions and new stiffness matrix for constructed damage state is obtained for damaged laminate. Afterward, some interrelationship constants, which only depend on the material properties of undamaged lamina, are derived. Using these interrelationship constants, a simple equation for Gibbs free energy is acquired. By differentiating the Gibbs free energy equation with respect to the delamination length, a simplified equation is obtained for evaluating the energy release rate, which can be applied for prediction of delamination formation. In addition, ANSYS finite element software is used to evaluate the damaged material properties and strain energy release rate of damaged laminates numerically. The obtained results show that there is an acceptable agreement between developed analytical and numerical methods with the difference less than 5%.