Mechanical Properties and Creep Behavior of Carbon Fiber Nano-Composites
Recently, it has been observed that surface modification of carbon nanotubes（CNTs）influences on CNT’s distribution among epoxy resin and affects the mechanical properties and electrical conductivities of CNTs. Owing to above-mentioned effects, carbon nanotubes treated with oxidizing in organic acids, a kind of surface modification, generates functional groups on the surface of CNTs taht is a major investigation in this study to enhance mechanical properties and electrical conductivities of CNTs. The influence of the different proportion contents of CNTs added into epoxy resin on mechanical properties and electrical conductivities of composites was investigated, and strength of material tested under different temperature environments was observed. Moreover, the creep behavior of carbon fiber（CF）/epoxy resin thermosetting composites tested under different temperature and stress were also concerned to be analyzed. The resulting creep behavior consists of only two stages, including primary creep and steady-state creep. The effects of creep stress, creep time, different humidity treatment on the various temperature creep of composites containing different proportion contents of CNTs were investigated. It is believed that the increased creep strains can be attributed to higher applied stresses, longer creep times, higher humidity, higher temperature and lower hardnesses. The test results also exhibit that mechanical strength and electrical conductivity increase with the increase of CNTs content added into composites. In the influence of temperature effect on specimen, because of different coefficient of expansion among matrix, fiber and CNTs, the overexpansion of matrix caused by high temperature results in crack occurred among matrix. From observation of the fracture surface by SEM image, the debonding occurs and longitudinal fibers are pulled out due to poor interfacial bonding of fiber and matrix, which also results in entire strength degeneration.
Zhong Cao, Lixian Sun, Xueqiang Cao, Yinghe He
Y. L. Li et al., "Mechanical Properties and Creep Behavior of Carbon Fiber Nano-Composites", Advanced Materials Research, Vols. 233-235, pp. 2794-2799, 2011