Rubber Containing Nanofibers and Their Ability in Structural Modification of CFRPs: A Summary

Rubber containing nanofiber is investigated as structural modifiers of carbon fiber reinforced polymers (CFRPs) to improve their delamination resistance. The ability to obtain long lasting nanofibrous shape from liquid nitrile butadiene rubber (NBR) has been demonstrated even without requiring instant cross-linking when a second component is used together with NBR in the process. The second component can be a thermoplastic which either melts, such as poly(e-caprolactone) (PCL), or holds steady, as poly(m-phenylene isophthalamide) (PMIA) or nylon 66, during CFRP curing process. Assuming that NBR is not crosslinked, during curing of low T_m thermoplastic-based rubber nanofibers, their morphology is lost, as for NBR/PCL, and both polymers blend with the surrounding epoxy resin thus leading to an outstanding toughening effect, but at the cost of the overall composite mechanical performance. When a second component is used which is preserved in nanofibrous fashion during curing (NBR/PMIA, NBR/nylon 66), instead, a good compromise is achieved, with still outstanding delamination hindering ability, together with almost fully preserved thermo-mechanical performances.