Modeling and optimization in manufacturing variable stiffness composite structures

Official URL: https://risc01.sabanciuniv.edu/record=b3210389

The advent of advanced composite manufacturing technologies has led to the mass production of composite laminates with curvilinear fibers, known as variable stiffness laminates (VS). VS laminates can be enhanced in structural properties by tailoring the in-plane fiber orientations compared to constant stiffness laminates (CS). However, the production of VS laminates is subject to challenges, such as wrinkles, gaps, and overlaps. This study presents a novel approach to designing VS laminates while taking manufacturing constraints into account. This study involves four main steps. As a first step, the composite panel is modeled using the spectral Chebyshev method as the solution method and the lamination parameters as the design variables. A gradient-based optimization algorithm is used to determine the optimum lamination parameters (LPs) in order to maximize the fundamental frequency. In the next step, the discrete fiber angles are retrieved from the optimum LP distribution. Then, the normalized-cut segmentation (NCS) method is applied to divide the discrete fiber domain into clusters according to predefined clustering parameters such as the minimum cluster population, the angular similarity index, and the spatial similarity index. Lastly, a parallel fiber path planning algorithm is implemented for both 2D and 3D structures that are designed to achieve zero gap overlap when laying fibers on a structure. Following initial fiber path propagation, a critical curvature analysis is performed in order to modify the designed fiber paths and prevent wrinkles from appearing during the manufacturing process. In order to demonstrate the effectiveness of the presented design framework, we conducted several case studies involving both straight and curvilinear fiber paths in clusters. It has been demonstrated that the designed VS composites significantly improve the dynamic performance of the structure. In comparison to an optimized composite structure with constant stiffness, a composite plate with variable stiffness and length ratio of 1 enhances the fundamental frequency of the structure by 25%, 18%, and 16% without manufacturing constraints, curvilinear fiber paths in clusters, and straight fiber paths in clusters, respectively.