A new perspective on the needle-puncture property of silkworm cocoons with a hierarchical multi-layer structure

Abstract In present study, we focused on the hierarchical needle-puncture properties of silkworm cocoon aiming to capture a clear regularity from the inside to outside. To realize this target, we firstly conducted the peeling operation manually on silkworm cocoon to get specimens of 7 layers, 8 layers, and 9 layers. Subsequently, we investigated the surface morphology of each layer and puncture resistance of each component layer to better understand the contribution of each layer. Next, mathematical statistical analysis and fracture morphology were combined to analyze the fracture as well as enhance mechanism which will benefit for further design of composites with high puncture tolerance. Finally, the results illustrate that the outmost layer suggests the strongest puncture resistance and the innermost layer depicts the weakest. Consequently, this work inspires a clear-cut frame to design a puncture resistant composite with explicitly hierarchical structure.