The effect of nanoclay reinforcement on the rolling contact fatigue behaviour of polyamide

Polymer nanocomposite has received great research interest in design of engineering components owing to its remarkable improvement in tribological characteristics. Rolling contact fatigue is a predominant failure mode of the many functional components like gears, bearings, cams, ball screw rods and rail wheels. Nanosize clay fillers were dispersed into the polymer using melt intercalation method to produce polymer nanocomposite material. Injection-molded disc-type specimens were made to run against each other on twin-disc test rig designed in-house. To understand the behaviour of the materials, rolling contact fatigue behaviour against different contact loads under constant speed were studied. Rolling contact fatigue testing of polymer nanocomposite has revealed significant difference from the pristine PA6 behaviour in failure modality and temperature rise. Addition of nanoclay to polymer although improved the modulus and strength of the nanocomposite, deteriorated the rolling contact behaviour. Rolling contact fatigue performance of PA6 was better than that of the clay-reinforced polymer nanocomposite under all tested conditions. Polymer nanocomposite materials have shown poor wear resistance as the specific wear rate was calculated to be higher for PNC materials under rolling contact fatigue conditions. Difference in surface temperature rise in PA6 and polymer nanocomposite has led to the different failure mechanism and reduction in rolling contact fatigue life of polymer nanocomposite materials.