Optimization of Long Anisotropic Laminated Fiber Composite Panels with T-Shaped Stiffeners

A method to optimise long anisotropic laminated fibre composite panels with T-shape stiffeners is presented. The technique splits the optimisation problem into two steps. At the first step, composite optimisation is performed using Mathematical Programming (MP) where the skin and the stiffeners are characterised by lamination parameters accounting 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 stiffened panel consists of a series of skin-stiffener assemblies or super-stiffeners. Each super-stiffener is further idealised as a group of flat laminated plates that are rigidly connected. The stiffened panel is subjected to a combined loading under strength, buckling and practical design constraints. At the second step, 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 numerical analysis methods such as Finite Elements (FE) at the first step, 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.