Postbuckling optimisation of variable angle tow composite plates

The potential for enhanced postbuckling performance of flat plates using variable angle tow (VAT), in comparison with conventional laminated composites, has been shown previously. This paper presents an optimization strategy for the design of postbuckling behaviour of VAT composite laminates under axial compression. The postbuckling performance of composite laminated plates for a given compression loading is assessed by studying both the maximum transverse displacement and the end-shortening strain. For the postbuckling analysis of VAT composite plates, an efficient tool based on the variational principle and the Rayleigh-Ritz method is developed. In the optimization study, a mathematical definition based on Lagrangian polynomials, which requires few design parameters, is used to define a general fibre angle distribution of the VAT plate. A generic algorithm is subsequently used to determine the optimal VAT configuration for maximum postbuckling performance. The optimization of square VAT laminates under compression loading for different in-plane boundary conditions is studied and compared with straight fibre designs.