Efficient strength optimization of variable stiffness laminates using lamination parameters with global failure index

A computationally-efficient strength optimization method tailoring novel composite laminates using lamination parameters is developed. The method adopts a global p-norm approach to aggregate local failure indices into a global failure index, based on the Tsai-Wu failure criterion. For design purposes, the novel composite laminates are characterized via lamination parameters that can subsequently be transformed into locally variable fiber orientations in an existing three-step optimization method. An elliptical formulation of the conservative failure envelope is applied to represent the Tsai-Wu criterion in terms of lamination parameters. A lamination-parameter-based two-level approximation for the global failure index is derived, which guarantees the anticipated conservativeness and convexity in a gradient-based optimization framework. Numerical results show that the computational efficiency of the proposed strength optimization method improves remarkably with a proper value of p, compared to the existing local-based min-max method. The method is also shown to be robust and generate converged optimum designs even in the presence of stress concentrations and singularities. (C) 2022 Elsevier Ltd. All rights reserved.

Automated summary

A computationally-efficient strength optimization method using lamination parameters has been developed for tailoring novel composite laminates. The method employs a global p-norm approach to aggregate local failure indices based on the Tsai-Wu failure criterion. The proposed method characterizes the laminates using lamination parameters and derives a two-level approximation for the global failure index, ensuring conservativeness and convexity in a gradient-based optimization framework. Numerical results demonstrate the improved computational efficiency compared to existing methods and the robustness of the method in handling stress concentrations and singularities.