Mechanical Performance Enhancement of Double‐Layer 3D Woven Spacer Foam Sandwich Panels: Design, Fabrication, and Numerical Analysis

ABSTRACT The core layer of 3D woven spacer fabric reinforced polymer composites (WSFC) is relatively weak, leading to limited mechanical properties. In this work, improvements in the mechanical properties of 3D WSFC were achieved by modifying the core layer structures, including foam filling, double‐layer stacking, and misaligned stacking. The results show that the flexural strength of 3D WSFC foam sandwich panels in the weft direction is significantly greater than that in the warp direction. Filling the core layer with epoxy microsphere foam and polyurethane foam enhances the warp direction flexural strength by 51.8% and 124.3%, respectively. Moreover, variations in core layer structure significantly influence the flexural behavior and damage modes of the 3D WSFC foam sandwich panels. The double‐layer structured 3D WSFC foam sandwich panels exhibit less damage than the single‐layer panels. When the core structure is misaligned, both types of 3D WSFC foam core sandwich panels show similar mechanical properties, significantly reducing the performance differences across directions. To further understand the mechanical response, macro/meso‐scale models of 3D WSFC foam sandwich panels with various core configurations were developed, enabling in‐depth analysis of stress distribution and damage mechanisms.