INCREASING MECHANICAL STRENGTH OF CARBON/CARBON COMPOSITES BY CONTROLLING THE ORIENTATION AND LENGTH OF CARBON NANOTUBES GRAFTED ON CARBON FIBERS

摘要

A lot of challenges still exist in reinforcing carbon/carbon (C/C) composites though so many efforts have focused on this issue over the past few decades [1, 2]. The greatest one is how to provide more substantial reinforcements than traditional methods through improving fiber/matrix (F/M) interfacial bonding only via treating carbon fiber surface. Recently, some researches [3 J have proved an effective method of reinforcing the F/M interface of fiber/polymer composites by grafting carbon nanorubes (CNTs) onto fibers. Illatively, the transfer of this technique should also generate some exciting results in reinforcing C/C composites. Although Gong et al. [4J have implied the clear improvement of F/M interface of C/C composite after grafting CNTs on carbon fiber, the corresponding mechanical properties of CNTs reinforced C/Cs are very rare [5], let along excellent reinforcements. Possible reasons for these problems are omnifarious, which has been involved in the issues such as efficient grafting on carbon surface and dispersion of CNTs, and so on. On the other hand, to maximize the performance of CNT reinforced C/C (CNT-C/C) composites, a big part of energies should be divided and paid on the work of CNT-morphology optimized tailoring, which could allow CNTs to reinforce the mutual interaction between fiber and matrix availably and meanwhile offer further benefits i.e. providing increased lateral support of the load-bearing fibers and influencing and stiffening the surrounding matrix at greater depth. In this work, CNTs, with different orientations and lengths, were grafted onto carbon fibers by a simple catalytic chemical vapor deposition (CCVD) respectively. And then they were used to reinforce C/C composites. Our aim is to evaluate the role of CNTs with different grafting morphologies in enhancing C/C composites. It is believed that this work can pave a meaningful way to maximize the excellent performance of CNT-C/C composites.