Fibers of thermoplastic polymer blends activate multiple interlayer toughening mechanisms

Interleaving fiber reinforced layered composites with thermoplastic veils is a strategy that has been examined by using electrospun fibers of homopolymers as well as their physical mixtures. Separate toughening mechanisms were activated by the individual presence of the physically mixed fibers in previous studies. Here, we show that it is possible to initiate a concerted action of these mechanisms by interleaving electrospun fiber veils based on blends of PCL and PA6 (80/20, 60/40 and 40/60). Blend composition was pivotal in activating different toughening mechanisms. Fiber debonding was unobstructed in PA6 interleaves in mode I; whereas PCL toughened the interfaces by plasticizing the epoxy. Debonding and effective bridging along the strong axes of fibers was only possible at a certain blend composition that permitted penetration of PCL into the epoxy matrix upon melting during curing and allowed these regions to retard debonding.