A comparison between the slitting method and the classical lamination theory in determination of macro-residual stresses in laminated composites

This study aims to use optimization to increase the design load of composite sandwich cylinders under external hydrostatic pressure. Unlike other studies that only consider buckling, this study took into account both buckling and material failure. MSC.NASTRAN was used for the finite element analysis, while a micro-genetic algorithm was used for the optimization. The finite element model was validated by comparison with the experiment results, and the result of the optimization using the finite element method was validated by comparison with the result of the feasible region analysis. Based on the optimization, as the thickness of the sandwich increases, the buckling load becomes larger than the material failure. Consequently, the optimum point is determined by material failure. The current results suggest that both the buckling and the static material failure should be considered in the design of the composite sandwich cylinder.