MECHANICAL PROPERTIES OF CARBON/CARBON COMPOSITES REINFORCED BY CARBON NANOTUBES WITH DIFFERENT EXTENDING LENGTHS

摘要

Carbon fiber (CF)-reinforced carbon composites (C/Cs) possess wide structural applications in aeronautics and astronautics [1]. Although excellent in-plane tensile properties have been achieved using various configurations of fiber preforms, the relatively weak compression and interlaminar properties dominated by the low-strength brittle carbon matrix significantly degrade the stability of C/Cs. Carbon nanotubes (CNTs) are regarded as the ideal secondary reinforcement, due to their excellent mechanical properties [2]. The use of nano-level CNTs in the micro-level CF preforms can provide the opportunity to improve the bonding state of fiber/matrix (F/M) interface and also to modify the microstructure of pyrocarbon (PyC) and then increase the structural continuity of C/Cs [3], improving their matrix-dominated mechanical properties. So far, CNTs with different morphologies, including fluff-like CNTs, curved CNTs, CNT thin-coating, randomly-oriented CNTs, and so on, have been grafted on the CFs to reinforce the C/Cs [4—7]. Although some promising improvements in matrix-dominated mechanical strengths are achieved, the effects of important parameters, such as dimensions of CNTs on the microstructure and mechanical behaviors of C/Cs have not yet been clarifies. In this report, curved CNTs with different extending length were in situ grown onto the CFs using injection chemical vapor deposition (ICVD) technique. Evaluation of CNT extending length on the microstructure and mechanical behavior of C/Cs was discussed.