Conical-shaped variable stiffness composite laminates: Design and fiber path planning

This study presents an innovative design methodology for conical-shaped variable stiffness composite laminates. It employs the spectral Chebyshev method to solve dynamic equations, optimizing lamination parameters to maximize fundamental frequency. Subsequently, the fiber angles at the sampling points across the domain are retrieved. In the final step, a custom normalized cut segmentation approach is proposed to partition the domain into clusters and delineate fiber paths based on discrete fiber angles, while satisfying the manufacturing constraints such as curvature, gaps, and overlaps. The effectiveness of the proposed design methodology is demonstrated through several case studies, where maximum enhancement in fundamental frequency for the same part weight is compared to optimized constant stiffness composite laminates. The results show that an enhancement of 16% is achievable for a variable stiffness laminate disregarding manufacturing constraints for the fully clamped case study. However, the improvements reduce to 12.6% and 14% (deviating from the ideal optimal fundamental frequency by 4.5% and 3.3%), respectively, once the manufacturable constant and curvilinear fibers in each cluster are computed. This work can lead significant advances of engineering applications by enabling the design of variable stiffness laminates with complex geometries improving mechanical performance and/or reducing structural weight compared to conventional laminates.