Optimization of long anisotropic laminated fiber composite panels with T-shaped stiffeners

A method to optimize long anisotropic laminated fiber composite panels with T-shaped stiffeners is presented. The technique splits the optimization problem into two steps. At the first step, composite optimization is performed using mathematical programming in which the skin and the stiffeners are characterized by lamination parameters accounting for their membrane and flexural anisotropy. Skin and stiffener laminates are assumed to be symmetric or midplane symmetric laminates with 0-, 90-, 45-, or - 45- deg ply angles. The stiffened panel consists of a series of skinstiffener assemblies or superstiffeners. Each superstiffener is further idealized 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 layups are obtained using a genetic algorithm and considering the ease of manufacture. This approach offers the advantage of introducing numerical analysis methods such as the finite element method at the first step, without significant increases in processing time. Furthermore, modeling the laminate anisotropy enables the designer to explore and potentially use elastic tailoring in a beneficial manner.