Optimization of hybrid aluminum/cfrp box beams

Hybrid structural components in which a principal aluminum structure is reinforced with unidirectional CFRP composite laminates are an effective way to meet the requirements of low weight, high strength and stiffness, relative ease of design and fabrication and good reliability. Designing such components must be done by a procedure appropriate to the material system, with a careful consideration of the failure modes and the possibility of optimizing the component. In this study we analyze the problem of minimum weight design of CFRP-reinforced thin-walled rectangular aluminum sections subjected to given strength and stiffness constraints. The problem is formulated within the framework of classical nonlinear optimization analysis. It is shown that at the optimum design various local failure mechanisms occur simultaneously, while stiffness rarely controls. Experimental results support the accuracy of the calculations and provide additional information on the flexural behavior of hybrid aluminum/CFRP members.