Mechanical properties and structure of silkworm cocoons: A comparative study of Bombyx mori, Antheraea assamensis, Antheraea pernyi and Antheraea mylitta silkworm cocoons

Environmental effects on the construction and physical properties of Bombyx mori cocoons

“…2) and the definition of layers in the cocoon. This observation suggests that methods aiming to distinguish individual cocoon 'layers', may not be transferrable across a wide range of environmental conditions [15,20,21]. An explanation for the differences in mechanical properties lies within the sericin.…”

“…When tested individually, silk fibres show considerable variation on intraspecific and interspecific scales and the rate of spinning has been shown to affect fibre structural and mechanical properties [13][14][15][16][17] and in particular the effect of degumming prior to use [18]. Beyond individual fibres, mechanical tests on the cocoon have been performed between cocoons produced by an individual silkworm [19], across different dimensions of the cocoon [15] and between individual layers of the cocoon [15,20,21].…”

Intrinsic tensile properties of cocoon silk fibres can be estimated by removing flaws through repeated tensile tests

“…The spun silk strand (bave), which contains two filaments, is laid continuously by a silkworm in a highly ordered manner due to its orchestrated movement [10]. We have observed that while silk gum anchors the already extruded strand to a surface during cocoon formation, the spatial movement of the spinning head exerts the drawing force to the newly extruded portion of the strand.…”

Silk cocoons as natural macro-balloon fillers in novel polyurethane-based syntactic foams

“…1) [17]. The columnar crystals (20e30 mm long) do not enhance interlaminar adhesion (in the outer layers) or fracture toughness, but owing to their high hardness of around 2 GPa, the crystals are known to improve the indentation hardness of the cocoon [18,19]. Our research group has not only previously evaluated the impact resistance and damage tolerance of cocoon shells, but has also developed stochastic models based on open-cell foam structures to study natural silkworm cocoon shells as model materials for the failure analysis of synthetic non-woven composites [19,20].…”

“…The high rigidity and compressive properties of G. postica cocoons in comparison to B. mori cocoons was primarily due to the former's higher apparent density resulting from its larger dimensions and higher wall thickness [18,19,34] (Table 1), which spread the load over a larger area. The larger bonding area in wild cocoons may also ensure effective stress distribution [18,19,34]. Moreover, the extensive coverage of micro-scale calcium oxalate crystals on the outer surface of the wild cocoon is thought to stiffen the outer layers (in comparison to the inner layers), particularly by filling pores between fibre bundles (Fig.…”