Carbon nanofibre reinforcement of soft materials

In elastomeric matrices carbon nanofibres are found to be twenty times more effective than carbon black as a reinforcing filler. In hard matrices, by contrast, reinforcement is minimal. Tensile and dynamic mechanical tests were performed to elucidate the mechanism of reinforcement in order to explain the superior performance in soft matrices. Small-angle neutron scattering and ultra-small-angle X-ray scattering were used to quantify filler morphology, which turns out to be the key factor that limits reinforcement potential. The presence of fractal cluster formed by agglomeration of the nanofibres reduces the effective aspect ratio of the nanotubes. Clustering, however, introduces a new reinforcement mechanism based on elastic deformation of the fibre clusters. This mechanism is operative in soft matrices but not in hard matrices, thus explaining the enhanced performance in soft matrices.