Improving compression-after-impact performance of carbon–fiber composites by CNTs/thermoplastic hybrid film interlayer

Multi-walled carbon nanotubes (MWCNTs) have been effectively dispersed with polyetherketone cardo (PEK-C)/dichloromethane by ball milling technique. Pure PEK-C film and MWCNTs hybrid PEK-C (MWCNTs/PEK-C) films with different MWCNTs content were made employing an solvent casting technology. Transmission electron microscope (TEM) showed the MWCNTs shortened by ball milling. The neat and nano-hybrid films were used as interleaves for carbon fiber/bismaleimide (BMI) composite laminates. C-scan results showed that impact damage area decreased for PEK-C film interleaved laminates and further reduced by modification of MWCNTs. The compression after impact (CAI) strength was significantly improved for interleaved composite laminates when compared to baseline composite laminate. Maximum improvement (∼33%) of CAI value was achieved by interlayer of hybrid film with 10 wt% MWCNTs. The toughening micromechanism of enhanced resistance to low-energy impact with the incorporation of MWCNTs were investigated based on scanning electron microscopic (SEM) images of the fracture surfaces of the tested specimens. It is suggested that thermoplastics, BMI particles and MWCNTs had combined action to reduce interlaminar impact damage and thus to improve CAI strength.