Simplified analytical approximations for scaled composite laminates under transverse loading

Delaminations caused by impact or indentation are a major cause of strength reduction in composite laminated structures. Since delaminations seldom occur in just one location through the thickness, the effect of multiple delaminations on the geometrical nonlinearity and response of scaled composite laminated plates subjected to a transverse concentrated load is studied here through analytical formulations. The scaling includes in-plane dimension scaling and sublaminate scaling based on a Reference plate with a stacking sequence of [45°/90°/0°/-45°]_2S. The analytical approximation obtained under point loading quasi-static indentation is also suitable for studying large-mass low-velocity impact or for experiment and laminate design. The analytical approximations were compared with axisymmetric finite element model and static indentation tests conducted in a previous study. The novel achievement of this work is that it includes analytical expressions to predict the evolution of damage and load-displacement curves as a simpler alternative to the complex nonlinear finite element models.