WrapToR Truss Stiffeners: Lightweight Reinforcement for Composite Skin Panels

This work introduces novel lightweight composite panel structures with high specific stiffness and strength, which exploit the exceptional performance of Wrapped Tow Reinforced (WrapToR) trusses. These trusses are used as panel stiffeners, by bonding them to face sheets in repeating grids. This produces an alternative to both traditional stringer reinforced panels and sandwich panels, with the potential for significantly increased mechanical performance. After introducing the concept, details on the fabrication of prototype panels with a cruciform truss reinforcement pattern are described. The manufactured panels are then characterized using a three-point bend test to determine stiffness properties. To benchmark the performance of the truss-stiffened panels structures, a comparative analysis is conducted using a low fidelity but conservative model for sandwich panel stiffness. It is found that the experimentally tested truss stiffened panels provide an 82.8% increase in stiffness at equivalent mass compared to a best-case sandwich panel. To further explore the design space of the truss stiffened panels, a simple parameter sweep is conducted using Finite Element Analysis to compare different configurations of truss variables. Pareto optimal results for mass and stiffness are shown, and specific configurations on the Pareto frontier are explored to highlight the impact of varying the four truss design variables.