The effect of particle addition and fibrous reinforcement on epoxy-matrix composites for severe sliding conditions

This paper reports production and tribological testing of epoxy-matrix composites for dry-sliding conditions. The examined composites are produced using the following components: epoxy resin (EP), glass fiber weave (G), carbon/aramid hybrid weave (CA), PTFE particles and nano-scale CuO particles. Friction, wear and interfacial temperatures are measured on a custom-built pin-on-disk apparatus using a steel disk as counterface. The performance of the two types of reinforcing weaves are compared at nine different combinations of contact pressure (p) and sliding velocity (image) also called image conditions. The purpose is to systematically compare the performance of the differently reinforced materials while going from mild to severe sliding conditions. It is found that the coefficient of friction (image) on average is reduced by 35% by substituting the glass fiber weave with the carbon/aramid weave. The latter, shows superior wear behavior at the six mildest image conditions with the wear rate (image) an average factor of 22 lower than the rates for glass fiber reinforcement. An effect of fiber orientation with respect to sliding direction is found for the glass fiber reinforcement. The best tribological properties are seen when the fibers are parallel and anti-parallel (P–AP) to the sliding direction compared to normal and parallel (N–P). Experiments with incorporating micro-scale PTFE particles and nano-scale CuO particles, respectively, into the epoxy resin along with the carbon/aramid weave shows no difference in friction but minor improvements in wear. When micro-scale PTFE particles are incorporated into the neat epoxy resin, i.e. without fibers, an increase in image and a decrease in image are measured. When the same is done with nano-CuO a deterioration of both friction and wear properties are seen. At the three roughest image conditions all tested composites show signs of decomposition. Despite this, glass fiber reinforcement has a relatively steady behavior while carbon/aramid reinforcement gives raise to a gradually increasing frictional force, which ultimately results in complete failure of the test-specimen.