Deformation mechanism and mechanical model construction for recycled regenerated silk fibroin/polyvinyl alcohol blended fibers

The mechanical properties of regenerated silk fibroin-based fibers have attracted much attention, but the related theoretical research and the mechanical model are insufficient. Thus, recycled regenerated silk fibroin (RRSF)/polyvinyl alcohol (PVA) blended as-spun fibers were taken as an example. Transformations of the apparent morphology, microstructure, and two-phase distribution of the as-spun fibers were explored at different tensile stages. The appropriate mechanical models were established with model formulas. The results showed that the RRSF component in the fiber gradually presented an axial fibril-like dispersion and split fragmentary areas under uniform stretching. Then, the PVA component undertook the external force, and ductile fracture finally occurred. At the micro level, the β-sheet content of the RRSF component reached a maximum of 54.7% at 50% elongation. The value of I⊥/I∥ reached the highest point (1.25) when stretched to 100%. The tensile process was divided into low-, negative-, and high-viscoelasticity deformation stages. Nonlinear spring or sticky pot elements were introduced to establish a two-element parallel mechanical model, and the fitting degree of the model formula was higher than 0.993.