Plastics Part Design: Low Cycle Fatigue Strength of Glass-fiber-reinforced Polyethylene Terephthalate (PET)

This paper summarizes our extensive investigation on the low cycle (up to N f 1 /4 5 10 4 , where N f is the number of cycles to failure) fatigue behavior of short glass-fiber-reinforced poly(ethylene terephthalate), or PET, thermoplastic [PET - Thermo plastic polyester for injection molding]. The modes of fatigue test include tension-tension, compression-compression, four-point bending (flexural) - all at frequency f 1 /4 1-3 Hz, and flexural fatigue at f 1 /4 30 Hz (ASTM D-671). All tests were stress-controlled with stress ratio R 1 /4 S min /S max 1 /4 0.1, except for flexural fatigue at f 1 /4 30 Hz where stress ratio R 1 /4 1. The fracture surfaces of tested specimens were analyzed using scanning electronic microscopy (SEM). The results from this investigation provide comprehensive, up-to-date information and recommendations concerning methods for fatigue testing of injection-molded specimens and models, prediction and optimization of low cycle fatigue properties that play a key role in determining a highly stressed plastic parts life and end-use performance, preselection of PET-based plastic for various industrial applications.