Enhancement of the Interlaminar Fracture Toughness of a Carbon-Fiber-Reinforced Polymer Using Interleaved Carbon Nanotube Buckypaper

Abstract

In this study, a carbon nanotube (CNT) buckypaper was interleaved in a carbon-fiber-reinforced polymer (CFRP) composite to improve the interlaminar fracture toughness. Interleaving the film of a laminate-type composite poses the risk of deteriorating the in-plane mechanical properties. Therefore, the in-plane shear modulus and shear strength were measured prior to estimating the interlaminar fracture toughness. To evaluate the effect of the buckypaper on the interlaminar fracture toughness of the CFRP, double cantilever beam (DCB) and end notch flexure (ENF) tests were conducted for mode I and mode II delamination, respectively. No significant change was observed for the in-plane shear modulus due to the buckypaper interleaving and the shear strength decreased by 4%. However, the interlaminar fracture toughness of the CFRP increased significantly. Moreover, the mode II interlaminar fracture toughness of the CFRP increased by 45.9%. Optical micrographs of the cross-section of the CFRPs were obtained to compare the microstructures of the specimens with and without buckypaper interleaving. The fracture surfaces obtained after the DCB and ENF tests were examined using a scanning electron microscope to identify the toughening mechanism of the buckypaper-interleaved CFRP.