Design of Optimal Hygrothermally Stable Laminates with Bending-Twist Coupling by Ant Colony Optimization

4The necessary and sufficient conditions for hygrothermal curvature stability of laminated composite plates have been derived in a prior publication and shown to be material independent. From within these conditions, various couplings are being investigated to determine any improvements over previously known optima. Bending-twist coupling has been investigated in previous work based upon a Sequential Quadratic Programming method to demonstrate the achievable level of coupling under the hygrothermal stability conditions. In this work, the Ant Colony Optimization is adopted as an alternative approach to reach global optima. Comparisons of resulting stacking sequences and associated level of coupling are provided. Results for laminates consisting of two through ten plies made of graphite/epoxy material are presented. The results suggest that the solution to the bending-twist coupling problem consist of multiple global optima. ACO was able to provide new global optimal solutions for laminates consisting of 8-10 plies.