Unique silk-carbon fiber core-spun yarns for developing an advanced hybrid fiber composite with greatly enhanced impact properties

Unique silk-carbon fiber (CF) core-spun yarns (SCCYs) were created via a scalable hollow spindle spinning method. As a novel type of hybrid fiber reinforcement, SCCYs were utilized to develop an advanced hybrid composite (i.e., silk-CF/epoxy resin composites, SCFECs). Avoiding traditional chemical modifications to fibers and matrices, the impact strength of SCFECs is substantially improved without compromising their static strength, ascribed to the distributed SCCYs in SCFECs with strategically located silk wraps at CF bundle-matrix interfaces that behave as the local energy absorbers and provide hoop confinement to individual CF bundles. Notably, the optimal impact strengths of SCFECs with only 5.6 vol% CF-5.2 vol% silk and 11.2 vol% CF-10.4 vol% silk are 50.4 and 64.4 kJ/m2, respectively (about 80% higher than the neat CF composites without silk). This work demonstrates new insights for building advanced hybrid composites with utilizing SCCYs, rendering them well-balanced overall mechanical performance and particularly promoted efficiency of the selected compatible fibers.