Silk cocoon (Bombyx mori): multi-layer structure and mechanical properties.

Bombyx mori cocoon is a natural composite made of silk fibre with a distinctive multi-layer structure that provides mechanical protection for its biological functions. Here we investigate the components, structure and mechanical properties of cocoon layers, and quantify the contributions of the multi-layer structure to the mechanical properties of cocoon. A better understanding of the multi-layer mechanism of a natural composite could help the further design of biomimetic multiscale artificial materials.