Thermal buckling response and fracture analysis for delaminated fiber reinforced composite plates under thermo-mechanical coupling

Fiber reinforced composites are often subjected to severe thermal-mechanical coupling loads. In order to predict the stiffness and strength of the designed composites, thermal buckling response of the delaminated fiber reinforced composite plates and fracture analysis along the delamination front under thermo-mechanical coupling are investigated based on the generalized layerwise plate theory. Delamination between individual layers is considered as discontinuities in the displacement field using Heaviside step functions in the finite element model of delaminated composite plates. Governing equations are derived using virtual work principle and fracture analysis is performed by calculation of the strain energy release rate along the delamination front by means of the virtual crack closure technique. The effect of laying angle, delamination size, and delamination position on the critical thermal buckling temperature of laminated composite plates are investigated. Numerical results reveal that the critical thermal buckling temperature is insensitive to the delamination size less than an 'irrelevant size' and then significantly decreases with the increase of delamination sizes. The inside delamination has a greater influence on the critical thermal buckling temperature than the outside delamination. The maximum values of strain energy release rate always occur in the 'equivalent material direction' when the delamination is located in the middle of composite plates, while it is determined by laying angle and delamination position together for non-middle plane delamination.