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

Abstract

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.

Keywords

poly(ethylene terephthalate)PET fiberglass reinforced orientation low cycle fatigue strength mechanical performance tensile flexural compressive

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