Effects of gaps and overlaps on the buckling behavior of an optimally designed variable-stiffness composite laminates – A numerical and experimental study

This paper reports an experimental and numerical investigation of the effects of gaps and overlaps on the buckling behavior of variable-stiffness composite laminates. In the experimental study, variable-stiffness composite laminates with a constant-curvature fiber path were manufactured and tested under uniaxial compression to failure with simply supported edges. The tested panels were optimized to simultaneously maximize the in-plane stiffness and the buckling load. Two manufacturing strategies – complete overlaps and complete gaps – were adopted to allow the independent effect of each type of defect to be investigated in isolation. In the numerical study, a two-dimensional finite element model was built using the commercial software Abaqus through a Python input script. A MATLAB routine was also implemented to localize the gaps and overlaps within the studied variable-stiffness laminates. A linear buckling analysis was performed to calculate the pre-buckling strength and the critical buckling load for each tested composite laminate. Thereafter, a nonlinear analysis using the Riks method was performed to predict the load–displacement relationship, considering the geometric imperfections of cured composite laminates. A good correlation was observed between the results obtained from the finite element simulations and from the experiments.