Manufacturing uncertainties and resulting robustness of optimized patch positions on continuous-discontinuous fiber reinforced polymer structures

Discontinuous fiber-reinforced Sheet Moulding Compound (SMC) in combination with continuous carbon fiber patches provide a high design freedom in combination with good weight-specific properties. However, the application of these materials requires a strategic and exact positioning of the patches, necessitating the consideration of unavoidable manufacturing defects during the design phase. Therefore, a workflow is proposed to evaluate the robustness of multi-objective patch optimization results using two robustness measures, the degree of robustness and robustness index. An efficient calculation of the robustness measures is achieved by replacing computational expensive simulation models with a Kriging surrogate model. Typical manufacturing deviations occurring during the patch positioning and moulding process are determined from experiments using active thermography. Finally, the proposed workflow is applied to the multi-objective optimization of two patches on a demonstrator under four-point-bending load. The resulting robustness measures can be used as a decision criterion for the selection of the best Pareto optimal solution. Furthermore, they can be used for the determination of the maximum occurring objective variation as well as the largest permissible manufacturing tolerances.