Electrospun short nanofibers to improve damage resistance of carbon fiber composites

Carbon composites are sensitive to matrix cracking, delamination, and fiber-matrix debonding induced by external transverse loading. Such invisible damages demand frequent non-destructive testing (NDT) owing to their tendency to propagate in brittle composites. Application of carbon composites in safety critical structures have urged researchers to design for superior damage resistance. Bulk modification of matrices through nanoparticles is one such technique that exploits high surface area and mechanical properties of nano-reinforcements to engineer desired interfaces and improve mechanical properties. This study adopts the same technique to investigate effect of electrospun nylon 6 short nanofiber addition on damage resistance of carbon fiber/epoxy composites. Different concentrations (0.05, 0.1, 0.2, and 0.4 wt% of epoxy) of short nanofibers were prepared to modify epoxy and fabricate carbon laminates. Quasi-static indentation tests confirmed improvement of 8.7, 8.8, and 53% in peak force, displacement and elastic toughness of carbon composites at optimum nanofiber concentration (0.05 wt%). External damage area marginally improved though directional damage growth was suppressed. Delaminated area reduced by 12.6% at optimum nanofiber concentration. Suppression of compressive fiber failure and enhanced interlaminar bonding were credited to offer superior performance. In general, development of nanofiber-rich zones declined the load bearing response above optimum concentration.