Fatigue Behavior of Engineering Polymers

In this paper, the basic definitions of the fatigue behavior of polymeric materials andthe thermal fatigue of polymers, which is due to their viscoelastic properties, arediscussed. Also, the mechanical fatigue of polymers from different aspects and the threestages mechanism include initiation, propagation and fracture have been discussed. Stressamplitude against number of cycles to fatigue failure curves are presented, which is oneof the ways to predict the fatigue behavior of polymers. Based on these curves, lifetimeand fatigue resistance are measured. The tests performed to predict the fatigue behavior ofpolymers are based on theoretical relationships. According to Paris law, the growth rate offatigue cracks is plotted in terms of stress intensity factor, which has a very effective rolein predicting the fatigue behavior of materials. Many factors can affect the fatigue behaviorof polymers, including various experimental and structural variables such as temperature,geometry, orientation, molecular weight, crosslinking, the presence of reinforcements,and environmental factors such as solvent and moisture. Due to the sensitive applicationsof engineering polymers such as polycarbonate (PC), polyoxymethylene (POM),polymethyl methacrylate (PMMA), polyamide (PA), polyphenylene oxide (PPO), andpolytetrafluoroethylene (PTFE), fatigue behavior is very important.