The Interfacial Shear Strength of Carbon Nanotube Sheet Modified Carbon Fiber Composites

Abstract

Carbon fiber reinforced polymer composites have low density and high tensile strengths. However, their compressive strengths are much lower than their corresponding tensile strengths due to fiber micro-buckling and interface failure between fiber and matrix. To address this issue, we report a method for fabricating carbon nanotube (CNT) sheet scrolled carbon fibers or fiber tows to improve the interfacial shear strengths. A CNT sheet is drawn from a drawable carbon nanotube forest grown on a silicon substrate, it is used to wrap around individual carbon fibers. The CNT wrapped carbon fiber is subsequently impregnated into a polymer to form a composite. Scanning electron micrograph shows that the wettability of CNT wrapped carbon fiber composite increases drastically in comparison with the composite without CNT, indicating significantly increased bonding between carbon fiber and polymer due to the addition of aligned CNT at the interphase. Fiber push-out and push-in nanoindentation characterization indicates increased interfacial shear strengths, consistently at over 80% with the use of wrapped aligned CNT sheet. The results from scrolling CNT sheet around individual carbon fibers to enhance compressive strengths indicate the potential performance enhancement of composites when this approach is scaled up.