Mechanical and tribological behaviours of epoxy hybrid composites reinforced by carbon fibers and silicon carbide whiskers

Abstract

Epoxy based hybrid composites were manufactured from epoxy-55 wt% carbon fiber (C/Ep) and C/Ep with 2.5 and 5 wt% silicon carbide whiskers (SiCw) by vacuum assisted resin transfer moulding. The effect of SiCw loading on mechanical properties as well as friction and wear behaviour of the hybrid composite has been discussed. In a comparison to C/Ep composite material without SiCw reinforcements there are modest improvements in the mechanical properties such as tensile strength, tensile modulus and flexural strength; but, a potentially significant decrease is demonstrated for the flexural modulus of these SiCw reinforced C/Ep hybrid composites. The experimental tribological data indicated that the C/Ep with SiCw composite showed excellent tribological properties. It was revealed that the fiber and filler worked synergistically to enhance the wear resistance and reduced the friction coefficient of the C/Ep hybrid composites. Further, for all composites, the friction coefficient increases with increase in load and sliding velocity. However, SiCw reinforced C/Ep exhibited considerably lower friction coefficient compared with C/Ep without SiCw, while SiCw as filler at a content of 5 wt% was effective in reducing the specific wear rate of C/Ep composite. The carbon fiber carried the major load between the contact surfaces and protected the matrix from severe abrasion of the counterface. At the same time, the exposed SiCw out of the epoxy matrix around the fiber inhibited the direct scraping between the fiber edge and counterface, so that the fibers could be less directly impacted during the subsequent sliding wear process and they were protected from severe damage. Further, the reinforcement effect of SiCw on epoxy might also restrict the crack initiation and propagation on the surface and subsurface of the composite, and therefore protect the matrix from fatigue failure during the sliding wear process. Mechanisms for the improved wear resistance were discussed with the help of scanning electron microscopy (SEM) observations.