Enhanced cryogenic interfacial normal bond property between carbon fibers and epoxy matrix by carbon nanotubes

The effect of the carbon nanotube (CNT) content on the carbon fibers (CF)/CNT-modified epoxy contact angle and on the transverse tensile strength at the cryogenic temperature (77 K) as an indication for the interfacial bond property of carbon fiber/epoxy composites are investigated. The results show that the contact angle reaches the minimum when the multi-walled CNT content equals 0.5 wt%. The composite transverse tensile strength shows a similar tendency as the contact angle with increasing the CNT content. The morphological observation of the fracture surfaces after transverse tensile testing is carried out and is consistent with the results for the contact angle and the transverse tensile strength. The transverse tensile strength is increased respectively by 29.3% and 51.7% at room temperature and 77 K at the 0.5 wt% CNT content compared to that of the pure epoxy case. Consequently, it is clear that the introduction of carbon nanotubes at a proper content into the epoxy resin can significantly enhance the cryogenic CF/epoxy interfacial normal adhesion property.