Tribological properties of epoxy nanocomposites

In our pervious studies [Z. Zhang, C. Breidt, L. Chang, F. Haupert, K. Friedrich, Enhancement of the wear resistance of epoxy: short carbon fibre, graphite, PTFE and nano-TiO2, Composites A 35 (2004) 1385-1392; L. Chang, Z. Zhang, C. Breidt, K. Friedrich, Tribological properties of epoxy nanocomposites. I. Enhancement of the wear resistance by nano-TiO2 particles, Wear 258 (1-4) (2005) 141-148], wear performances of a series of epoxy-based nanocomposites were systemically investigated by a pin-on-disk apparatus under different sliding conditions. The addition of spherical TiO2 nanoparticles (300 nm in diameter) was found to be able to apparently reduce the frictional coefficient, and consequently to decrease the contact temperature and wear rate of fibre reinforced epoxy composites. To promote this conclusion, the present paper intends to further understand the wear mechanisms involved in micro- and nanoscales. Based on a scanning electron (SEM) and an atomic force (AFM) microscopy observations of the worn surfaces, a positive rolling effect of the nanoparticles between the material pairs was proposed, which led to the remarkable reduction of the frictional coefficient. In particular, this rolling effect protects the short carbon fibres from more severe wear mechanisms, especially at high sliding pressure and speed situations. In order to validate the assumption proposed, the influence of the counterpart roughness on the wear performance were carried out as well.