Effect of electrospun polysulfone/cellulose nanocrystals interleaves on the interlaminar fracture toughness of carbon fiber/epoxy composites

Cellulose nanocrystals (CNC) were derived from microcrystalline cellulose (MCC) by sulfuric acid hydrolysis. The mechanical and fracture properties as well as fracture morphologies of CNC/epoxy (CNC/EP) composites with different CNC loadings were studied. A thermoplastic polysulfone (PSF) was added to toughen the epoxy. During the curing of PSF/EP composites, two different phase separation processes would occur due to the variation of the amount of PSF in the PSF/EP blend. The effects of CNC and PSF on the elastic modulus, strength and fracture toughness properties of the ternary PSF/CNC/EP composites were also examined. Electrospinning technique was successfully used to fabricate PSF/CNC nanofibrous membranes as an interleaf inserted into the mid-plane of the CF/EP composite laminates to increase the interlaminar fracture toughness. The results showed that after interleaving with the PSF/CNC nanofibrous membranes, mode I and mode II interlaminar fracture toughness values were enhanced compared to the non-interleaved CF/EP with neat epoxy or CNC-modified epoxy matrix as well as interleaved CF/EP laminates with PSF nanofibrous membranes. The toughening mechanisms of hybrid PSF/CNC nanofibrous membranes were examined based on the fracture surface morphologies of the composites.