Mechanical properties of Bombyx mori silkworm silk fibre and its corresponding silk fibroin filament: A comparative study

Bombyx mori silkworm silk fibre is recognized as a kind of natural biological composite materials. From the view of composite materials science, we carried out systematic tensile tests to study mechanical properties and their variations along the length of silkworm fibre (namely silk bave, composite material) and its corresponding silk fibroin filament (namely silk brin, reinforcement phase) of three complete cocoon silks. The factors affecting the mechanical properties were further discussed, including the size, sericin weight content and β-sheet content. Our experimental results and statistical analyses with the coefficient of variance and two-parameter Weibull function all revealed the following: First, silk brin displays smaller variations in the diameter and mechanical properties, compared to those of the bave. Second, mechanical properties of sericin (matrix phase in silk fibre) were estimated accordingly with the mixture law of composite materials. Third, strength and toughness of silkworm silks have trends of growth with the decreases in the diameter and sericin weight content, or increase in the β-sheet content. Fourth, the relatively comprehensive database on mechanical properties of silkworm silk (bave and brin) was obtained concurrently. The research might help in better understanding mechanical properties of silk fibres and their future applications.