Mechanical Properties of CFRP Composites with CNT Film Interlayer under Different Strain Rates

Carbon nanotube film prepared by floating catalyst chemical vapor deposition (FCCVD) method was used as interlayer toughening material for carbon fiber reinforced laminated composites. The carbon nanotube film/carbon fiber/epoxy hybrid (CNTF/CF/EP) composites were prepared by hot pressing and cut into two dimensions respectively for compression and type II fracture toughness test. It has been observed that the type II fracture toughness is improved by 60% due to the carbon nanotube interlayers. Scanning electron microscope results suggest that the bridging of matrix cracks by carbon nanotubes leads to a higher type II fracture toughness. The results of compression experiments indicate that the compressive strength in both in-plane and out-of-plane directions is enhanced to some extent under quasi-static compression due to the carbon nanotube interlayers. Moreover, the enhancement in compressive strength which is as high as 9% out-of-plane direction can be achieved under high strain rates after modifying the interlayer structures with carbon nanotubes. However, there is no increase of compressive strength during dynamic compression in in-plane direction, and the fracture morphology shows that the primary reason is due to the internal delamination of the carbon nanotube films.