Effect of grain fractions of crushed carbon foam on morphology and thermomechanical and tribological properties of random epoxy-carbon composites

The effect of dimension of carbon foam (CF) grains used as a filler of epoxy matrix on the morphology and thermomechanical and tribological properties of final composites was described. The carbon foam proposed as particle reinforcement of composites was prepared from epoxy resin of diglycidyl ether of bisphenol A type cured with phenol-formaldehyde resin (novolac) in a self-foaming process followed by carbonization. Structures of the carbon foam filler and resultant composites were studied by microscopic and spectroscopic methods. Three different carbon foam grain fractions, below 200 μm, 200–315 μm and below 315 μm, keeping CF porous structure and specific properties, were used to obtain new composite materials. There were observed good quality dispersion of CF grains in epoxy matrix and excellent adhesion at interfacial areas, regardless of carbon foam fraction. In the effect, these composites have enhanced thermomechanical and tribological properties and relatively low density compared to carbon-polymer composites produced so far. It was found that all CF fractions used reduced friction coefficient of resultant composites compared to pure epoxy matrix, however the influence of individual filler fraction on composite's COF was different. The morphology of worn surfaces of epoxy composites after friction tests showed that the effect depends on grain fraction of CF filler as well as on the load used.