Buckling optimization of variable angle tow panels using exact strip models

A minimum-weight optimization strategy for Variable Angle Tow (VAT) panels subject to buckling and manufacture constraints is presented. The optimization is performed using a fast-running optimization package which employs exact strip analysis for buckling and a gradient-based optimization method. A new VAT panel manufacturing method providing good quality, Continuous Tow Shearing (CTS), is considered in the optimization strategy, where variable thickness occurs due to the shear deformation of dry tows. Optimum designs of VAT panels are obtained and compared with panels without thickness variation. Different panel boundary conditions are investigated and discussed. The results show that boundary conditions have dramatic effects on optimum fiber paths. Over 20% weight-saving is obtained for the optimization strategy with thickness variation compared with the design without thickness variation. The buckling strains are reduced to a practical level when the thickness variation is considered in the optimization. The buckling loads and mode shapes obtained from the exact strip method are in a good agreement with the finite element results. The proposed optimization strategy is efficient, robust and produces well-converged designs.