An Investigation into the Fatigue Mechanism of PET Tire Cord in the Goodrich Block Fatigue Test

The Goodrich block fatigue test is commonly used to determine the (compression) fatigue behavior of tire cord in rubber. An investigation has been conducted into the origin of the loss of cord strength under different load conditions and at different running times. To this end the retained strengths and the force-strain curves of the fatigued cords were measured. The location of the cord fractures and a SEM analysis provided valuable extra information about the fatigue mechanism. The strength loss of the cords appeared to be mainly caused by the strength loss of the filaments. Changes in cord geometry and filament interaction occurring during the fatigue process play no or a very small role in the loss of cord strength. Depending on the load, the filaments show bending, tension-tension, and fretting fatigue damage. The severest fatigue load seems to be high tension combined with a certain amount of compression.