Design optimization of fiber reinforced plastic composite shapes

A global approximation method to optimize material architecture and cross-sectional area of new fiber reinforced plastic (FRP) composite beams is presented. The sections considered are intended for applications in short-span bridges. The beams are subjected to transverse loading, and the optimization constraints include deflection limit, material failure, and elastic buckling. Assuming a laminated structure for the pultruded FRP shapes, experimentally-verified micro/macromechanics models are used to predict member structural behavior. The design variables include the cross-sectional geometric dimensions and the material architecture. The constraint functions are defined through a global approximation at a number of design points, and the approximate constraint equations are obtained through multiple linear regressions and are defined as power law functions of the design variables. The proposed method can concurrently optimize the dimensions and material architecture of a given shape, and as an illustration, a new winged-box (WE) shape is optimized. The present optimization approach combined with existing knowledge on FRP shapes can be used to develop various new shapes and to create a new family of efficient FRP geometries for the civil structural market.