Local optimisation of long anisotropic laminated fibre composite panels with T shape stiffeners

A method to locally optimise long anisotropic laminated fibre composite panels with T shape stiffeners is presented. The technique splits the optimisation problem into two levels. At the first level, composite optimisation is performed using mathematical programming (MP), and the skin and stiffeners are modelled using lamination parameters that account for their membrane and flexural anisotropy. Skin and stiffener laminates are assumed to be symmetric, or mid-plane symmetric laminates, with 0, 90, 45, or -45 degree, ply angles. The skin-stiffener configuration is further idealised as a group of flat plate laminates that are rigidly connected. The panel is subjected to a combined case of loading under strength, budding and manufacturing constraints. At the second level, the actual skin and stiffener lay-ups are obtained using a genetic algorithm (GA) and considering the ease of manufacture. This approach offers the advantage of introducing accurate analysis methods such as finite elements at the first level, without significant increases in processing time. Furthermore modelling the laminate anisotropy enables the designer to explore and potentially use elastic tailoring in a beneficial manner.