Multiobjective material architecture optimization of pultruded FRP I-beams

This paper presents the application of micro/macromechanics models and optimization techniques for the optimum design of pultruded glass fiber-reinforced plastic composite I-beams with respect to material architecture: fiber orientations and fiber percentages. The beams are subjected to transverse loading, and beam deflection, buckling resistance and material failure are considered as multiple objectives (criteria) in the optimization process. Assuming a symmetrical laminated structure for the pultruded sections, experimentally verified micro/macromechanics models are used to predict ply properties, beam member response and ply strains and stresses. The Tsai-Hill failure criterion is used to determine first-ply-failure loads. Considering the coupling of lateral and distortional buckling, a stability Rayleigh-Ritz solution is used to evaluate the critical buckling loads for pultruded I-beams, and the results are verified with finite element analyses. A multiobjective design optimization formulation combined with a global approximation technique is proposed to optimize beam fiber architecture, which can greatly enhance the load carrying capacity of a section. The optimization procedure presented in this paper can serve as a practical tool to improve the performance of existing fiber-reinforced plastic without changing the current geometries.