Mechanical Properties of CNT/CNF Grafted Woven Carbon-Epoxy Composites

CNT/CNF grown on fabric can be later used to produce the composite plates through resin transfer molding or autoclave methods. Since the CNT/CNFs on the fabric will not cause a problem like increasing resin viscosity, they will clearly show a more homogenous distribution. By growing CNT/CNFs on fabric, it is possible to reach high ratios like 10%. However, potential problems during production of composite at high CNT/CNF ratios using such a technique remain unknown. This study examined basic mechanical properties and damage development properties of composite plates produced with CNT/CNF grown on 2×2 twill woven carbon fabric and compared the results with composite materials without carbon nanotubes. CNT/CNF grafting at high amount causes a CNT forest around the fiber and this causes significant limitations in composite material production. Due to increased distance between the fibers, local fiber volume fraction decreases within the yarns. Fiber volume fraction was found to decrease by 2.7-6.2 % according to CNT/CNF ratio. The results revealed that there were significant decreases in mechanical properties and characteristic strain values where damage initiation and progression of the composite samples produced from carbon nanotubes grown on fabrics. It was found that Young's modulus values decreased by 15-17%. Characteristic strain values where damage threshold decreased by 36-53%. It was concluded that decreased local fiber volume fraction and low fiber-matrix interface bonding were the main cause for this situation. Moreover, it is believed that the one of the most important factor that might cause these limitations is lack of adequate wetting of fiber surfaces and low fiber-matrix interface bonding.