Composite sepiolite/chitosan layer-by-layer coated flexible polyurethane foams with superior mechanical properties and energy absorption

•Design of polyurethane foam composites with naturally abundant sepiolite nanoclay and biopolymer chitosan via simple and facile layer-by-layer coatings.•The coatings reinforce the foam skeleton, resulting in a 200% improvement of the Young’s and dynamic moduli compared to untreated foams.•Transmitted impact forces are reduced by 50% with six bilayer coatings, demonstrating an improved impact energy dissipation.•Detailed discussions are provided about the deformation mechanisms and enhancement of the quasi-static and dynamic mechanical performance.