Creep-fatigue interaction and thermo-mechanical fatigue behaviors of thermoplastics and their composites

Creep-fatigue interaction and thermo-mechanical fatigue (TMF) behaviors of injection molded thermoplastic composites were investigated. Talc-filled polypropylene and short glass fiber reinforced polypropylene, polyamide-6.6, and a blend of polyphenylene-ether and polystyrene were used for the experimental study. Trapezoidal load signal with hold time periods was used for the creep-fatigue testing. Effects of temperature, frequency, load level, and hold-stress position on creep-fatigue interaction behavior were studied. In-phase TMF tests were conducted on polyamide-based composites for the temperature variation between 85 and 120 °C. Significant non-linearity was observed for the interaction of creep and fatigue damage. The applicability of Chaboche non-linear creep-fatigue interaction model to predict creep-fatigue and TMF lives for thermoplastic composites was investigated. A frequency term was added to the model to consider the beneficial effect of increased frequency observed for some thermoplastics. More than 90% of the life predictions by the Chaboche model were within a factor of 2 of the experimental life for both creep-fatigue and TMF test conditions.