I am co-author on a paper in the Journal of Experimental Biology on the impact behaviour of moth silk cocoons. The paper is part of then DPhil student Fujia Chen’s comprehensive study on the structure and material properties of a range of silk cocoons of Lepidoptera. The paper focuses on the anti-predatory function of the cocoons of three different moth species: the domesticated silk moth Bombyx mori, the Chinese Tussah moth Anthereae pernyi and the emperor gum moth Opodiphthera eucalypti from Australia. My main contribution was in generating the simple finite element model (using ABAQUS) that we used to extrapolate general findings on the importance of silk, sericin and geometry from the experimental stress-strain data and scanning electron microscopy observations.
Chen, F., Hesselberg, T., Porter, D. and Vollrath, F. (2013). The impact behaviour of silk cocoons. Journal of Experimental Biology 216: 2648-2657.
doi:10.1242/jeb.082545.
Abstract
Silk cocoons, constructed by silkmoths (Lepidoptera), are protective structural composites. Some cocoons appear to have evolved towards structural and material optimisation in order to sustain impact strikes from predators and hinder parasite ingress. This study investigates the protective properties of silk cocoons with different morphologies by evaluating their impact resistance and damage tolerance. Finite element analysis was used to analyse empirical observations of the quasi-static impact response of the silk cocoons, and to evaluate the separate benefits of the structures and materials through the deformation and damage mechanism. We use design principles from composite engineering in order to understand the structure–property–function relationship of silkworm cocoons. Understanding the highly evolved survival strategies of the organisms building natural cocoons will hopefully lead to inspiration that in turn could lead to improved composite design.
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