Spring-like sandwich foam composites reinforced by 3D Concave-Convex structured fabric: Manufacturing and low-velocity cushion response

In order to solve the problems of poor mechanical properties and incapable reuse for single cellular foam, this study proposed low-cost spring-like sandwich flexible foam composites (SFFCs) with a 3D resilient concave-convex structured fabric core (RCFC) and two gradient-structured styrene-ethylene/butene-styrene copolymer (SEBS)-g-maleic anhydride (MAH)-filled polyurethane (PU) foam faces through two-step foaming. RCFC plied with different sizes and distances constituted warp-knitted spacer fabrics (WKSF) sealed between two layers of low-melting polyester nonwovens through thermal bonding. The effects of SEBS-g-MAH content and volume content of RCFC cubes on compression and dynamic low-velocity impact properties were explored at different impact energy levels. At 3:4 (wt%) ratio of the upper-to-lower SEBS-g-MAH content faces and at 0.4 ratio of WKSF-to-PU volume ratio, the resultant SFFCs showed a compression stress of 68.4 kPa (40%) and absorbed up to 98% of impact energy under 16 J. After five cycles of impact, this sandwich foam composite maintained 98% absorption of impact energy, demonstrating excellent spring-like dynamic-impact-recovery property. Overall, this study provided a novel structure design for lower cost, higher-performance recycling cushion materials in industrial construction, transport packaging, and sports fields.