One‐step in‐situ growth of CNTs on oxidized carbon fiber: Effects of catalyst concentration and growth time on mechanical properties of carbon fiber

Abstract Chemical vapor deposition (CVD) method was performed to grow carbon nanotubes (CNTs) on oxidized carbon fiber (CF). First, CF was oxidized by a simple and gentle way to increase the number of active groups and the optimal treatment time was determined. Then, effects of catalyst concentration and growth time on morphologies and loading amount of CNTs, the properties of CF/CNTs reinforcements, and the interlayer properties of CF/CNTs composites were explored. When the catalyst concentration and growth time were controlled at a reasonable level, CNTs can be uniformly grown on the CF surface. The interlaminar shear strength (ILSS) was characterized and the fracture surfaces of CF/CNTs composites were observed. The results demonstrated that when the catalyst precursor was kept at 0.05 mol/L and the growth time was controlled at 10 min, CNTs had the best strength effect and the ILSS increased by 30.25% compared to that of composites without CNTs. The fracture surface showed that CNTs can penetrate the matrix at the interface and enhance the interface through mechanical interlocking effect. The CNTs‐induced interphase allows the stress inside the composites to propagate continuously between resin and fibers, thereby heightening the load carrying capacity. Highlights A simple and gentle way was performed to activate CF without strength reduction. The influence mechanism of various parameters was revealed in detail. The mechanism of CNTs enhancing the interface was revealed.