Bistable characteristics of unsymmetric cross-ply composite laminates considering different boundary shapes

The aim of this paper is to study the bistable characteristics of unsymmetric cross-ply composite laminates induced by thermal stress during the curing process when considering different boundary shapes. The changes in geometry for five types of planform shapes, have been focused, which are named rectangular planform (RP), elliptical planform (EP), trapezoidal planform (TP), diamond planform (DP) and cruciform planform (CP) respectively. The parameters that characterize the bistable performance of the laminates, including the principal curvature and snap load, were measured. The principal curvatures in different stable configurations were determined with analytical, numerical, and experimental methods, and the load-displacement curves in the snapping process were successfully obtained. Moreover, the boundary effect caused by the difference in planform shapes, which cause the local curvature of the bistable composite laminate to change, were also discussed. Predictions from an analytical shell model are verified through comparisons with nonlinear finite element simulations and experimental test results.