Design and fabrication of variable stiffness composite laminates with enhanced dynamic behavior

Design of variable stiffness (VS) laminates, featuring curvilinear fiber paths, requires efficient methodologies to attain structural performance levels beyond those of conventional constant stiffness (CS) composites. However, optimization and fabrication of VS laminates pose significant challenges. This problem is addressed in the present study, where lamination parameters (LPs) and spectral Chebyshev approaches are incorporated to obtain a multi-step design framework for symmetric and balanced composites. Initially, master points were defined to attain optimal LP distributions, which were subsequently used to retrieve the discrete fiber angles. Then, to obtain the continuous fiber paths, streamline and equidistant fiber path planning methods were implemented. For modal testing, laminate samples with the optimal fiber paths were fabricated via the automated fiber placement technique. The results show that the designed VS panels provide up to 8% performance improvement over optimal CS laminates. The experimental fundamental frequencies were found to be around 20% lower than the simulation results on average.