Multi-objective and multi-constraint design optimization for hat-shaped composite T-joints in automobiles

This study presents a multi-objective design optimization methodology on geometry and lay-ups for carbon fiber reinforced plastics (CFRP) T-joints in automobiles to achieve car body lightweight design. The CFRP T-joint was subjected to out-of-plane bending load using experimental method, and a finite element analysis (FEA) method was developed to simulate full failure procedure in the hat-shaped composite T-joint. A multi-objective and multi-constraint design optimization problem was then formulated to fmd optimum geometry and lay-ups of the composite T-joint. The non-dominated sorting genetic algorithm II (NSGA-II) was introduced to search for global optimum solution, and radial basis function (RBF) approximations for the objective functions were applied to reduce the computational cost. An original method was proposed for the initialization of the optimization that significantly accelerates the search for the Pareto front. The proposed method was validated by an obtained optimum design of a composite T-joint with reduced weight and improved overall stiffness and strength behavior, and can thus provide a guidance in practical vehicle composite joint design.