Rubbery nanofibrous interleaves enhance fracture toughness and damping of CFRP laminates

Rubbery electrospun nanofibers represent a smart way for hindering delamination and enhancing damping capacity in Carbon Fiber Reinforced Polymer (CFRP) laminates, which are two of the most serious drawbacks hampering their use. Nitrile Butadiene Rubber / Poly(ε-caprolactone) (NBR/PCL) blend nanofibers,with 20‐40-60%wt of not crosslinked NBR,were interleaved in epoxy-based CFRPs to evaluate their effect on the final composite performance. CFRPs with rubbery mats show a significant increase of the energy release rate in Mode I, both at initiation and propagation stages (+480% and +340%, respectively), thanks to NBR/PCL blend ability to promote high matrix toughening of the fragile epoxy resin. In Mode II a maximum improvement of about 30% was achieved. The presence of highly damping NBR component widens the composite energy dissipation window below room temperature, enhancing the CFRP damping. Similar results were obtained with two different epoxy resins, and the effect of the layering sequence was also discussed. NBR percentage in nanofibers and nanofibrous mats amount may strongly affect the CFRP maximum operating temperature. Nanofibers can be positioned, during lamination, in the critical regions where interlaminar stresses are mostly concentrated due to geometric discontinuities providing a flexible approach to localized modification of laminates.