Optimization design and analysis of stiffened composite panels in post-buckling under shear

In order to make full use of post-buckling load-bearing capacity of stiffened composite panel, it is meaningful to carry out research about the optimization strategy of stiffened composite panel especially in terms of its post-buckling behavior. The geometry parameter's influence on the buckling and post-buckling behavior of a bidirectional stiffened composite panel under in-plane shear is discussed in detail in this paper. Multi-level optimization including post-buckling capacity for composite stiffened panels under in-plane shear is presented in this article. In the 1st stage optimization, the geometry parameters are chosen as the design variables and the response surface method (RSM) is utilized to establish the global approximate function of the structure's post-buckling response. Results showed that the width and density of the stiffeners have important influence on the buckling bearing capacity. In the 2nd stage optimization, genetic algorithm (GA) is applied to optimize the stack sequence of the composite plies. The optimized structure shows a level of buckling displacement 8.86 times higher than that observed in the original panel and the mass decreased by 3% at the same time. The buckling mode transforms from early local buckling to global buckling, and the ultimate load capacity has also improved by 8.7% at the same time. Genetic algorithm dealing with the traveling salesman problem (TSP) is modified to solve the stack sequence optimization problem with fixed thickness. The optimized buckling eigenvalue has improved by 12.76%, which proves the validity and feasibility of the algorithm.