Buckling of optimised flat composite plates under shear and in-plane bending

Design rules based on theoretical solutions, which allow the prediction and understanding of the buckling and post-buckling behaviour of homogenous thin plates, exist for only a limited number of simple loading and boundary conditions due to the complexity of the equilibrium equations that describe the problem. When considering fibre composite plates, this issue is exacerbated by the inherent coupling between bending and extensional strains due to unsymmetric lamination, which results in three eighth order coupled partial differential equilibrium equations. This paper details a series of tests carried out to investigate the behaviour of a number of optimised fibre composite plates of differing geometry, simply supported along two edges and built in along the other two, subject to a varying combination of shear and in-plane bending, for which no theoretical solution exists, and assesses the suitability of analytical techniques and finite element analysis to predict this behaviour.