Abstract Silk cocoons of the domesticated silkworm Bombyx mori exhibit exceptional mechanical performance, serving as natural protective casings evolved over millennia to resist environmental threats and predation. This review critically examines the relationship between the cocoon’s molecular composition, hierarchical architecture, and its multifunctional mechanical behaviour. We begin by reviewing the primary and secondary structures of silk proteins, particularly fibroin and sericin, and their contribution to β-sheet crystallinity and tensile strength. At larger length scales, the anisotropic, multilayered structure of the cocoon wall demonstrates a strategic gradation in porosity, fibre density, and mechanical stiffness from outer to inner layers, supporting a synergistic defence strategy. Mechanical tests reveal notable resistance to tensile, tearing, stabbing, and puncture loads, with measured values that at times, outperform synthetic polymers, foams, and textiles. Finite element simulations further elucidate the cocoon’s stress redistribution mechanisms under a range of loading scenarios. Drawing from these insights, this review identifies critical knowledge gaps, particularly in interfacial mechanics, environmental effects, and hierarchical modelling, and outlines promising directions for bioinspired material design. We find that the B. mori cocoon is a model of evolutionary optimisation, and a blueprint for next-generation damage-tolerant structures.
Rehman et al. (Sat,) studied this question.