Photothermal Polyurethane Composite Foam: Enhanced Bionic Honeycomb Columnar Structure, Expanded Polystyrene Granules, and Spacer Fabric for Body Protection

Single polyurethane (PU) foams exhibit poor energy absorption, short service life, and are prone to damage under impact, which significantly limits their practical applications. In this study, inspired by the sheath wings of beetles, a bionic honeycomb columnar‐structured PU foam is developed. To further enhance its mechanical performance, the foam is reinforced with expanded polystyrene (EPS) particles and spacer fabrics. Additionally, a titanium nitride photothermal functional layer is applied to the surface to endow the material with photothermal properties. The mechanical properties, photothermal performance, cost‐efficiency, and human wearability of the composite PU foam are systematically investigated. The results demonstrate that the composite PU foam exhibits excellent mechanical strength and superior photothermal effects. Cost analysis reveals a 54% reduction compared to the D3O intelligent impact protection material, highlighting its economic advantage. Moreover, the material shows good softness and conforms well to the human knee, offering enhanced comfort during physical activity. These findings provide a novel strategy for developing sports knee pad materials suitable for cold environments.