ENHANCING THE INTERLAMINAR SHEAR STRENGTH OF UNIDIRECTIONAL CARBON FIBER REINFORCED PLASTIC (CFRP) LAMINATE USING A NANOFIBER Z-THREADING STRATEGY

摘要

Traditional carbon fiber reinforced plastic (CFRP) laminates without z-directional fiberreinforcement are vulnerable to matrix-sensitive damages including the interlaminar shear failure. It was hypothesized that long carbon nanofibers (CNFs) zig-zag thread through multiple layers of carbon fibers along the z-direction could form an interlocked multiscale fiberreinforcement network, therefore, enhance the interlaminar shear strength (ILSS) of the CNF zthreaded CFRP laminate. To find the answer, the “Double-Notch Shear Test” (ASTM D3846) was performed on the CNFs z-threaded unidirectional CFRP laminates. The CNFs z-threaded CFRP prepreg was manufactured by flow-transferring a resin film, containing 1 wt% electricalfield- aligned CNFs, into a dry unidirectional carbon fabric. The prepregs were stacked and cured into a laminate using an Out Of Autoclave-Vacuum Bag Only (OOA-VBO) process. Benchmarked with the ILSS of the control CFRP laminates, the CNF z-threads added a statistically substantial improvement to the CFRPs with an increased mean by +35.15 % and a reduced uncertainty (i.e., coefficient of variation) by -47.56 %. Oppositely, unaligned CNFs added to CFRPs yielded a negligible change in the mean and a substantially worse uncertainty. A microscopic morphology study was performed on the CNFs z-threaded CFRPs to understand the roles of the CNF z-threads in the interlaminar shear fracture mechanism.