Variable thickness design for composite materials using curvilinear fiber paths

Abstract

Carbon fiber reinforced plastic (CFRP) laminates are often used in a quasi-isotropic manner, such as in cross-ply lamination; thus, the mechanical properties of the CFRP cannot be fully exploited. In this study, we proposed a carbon fiber design method, which uses fiber orientation and thickness as the lamination parameters, where the fiber orientation is determined using the principal stress direction and the fiber thickness is determined by iterative calculations of the maximum stress theory using the bisection method. The method also accounts for manufacturability by considering fiber bundles and modifies the fiber orientation and thickness accordingly. As a result of implementing this method, the weight of wing plate model was reduced by approximately 5% with a failure index of approximately 0.7 compared with that using the constant thickness linear lamination model. Thus, the weight can be reduced while maintaining the strength, which may be useful for further weight reduction of conventional CFRP parts.