Fatigue Life of Refurbished Fiber Reinforced Thermoplastics

This study contributes basic knowledge in the field of fatigue testing for refurbished fiber reinforced thermoplastics (FRTP). In a first step quasi-static tensile test were performed. From the tensile tests stress amplitude levels are retrieved for fatigue tension-tension test with a stress ratio of R = 0.1. Fatigue tests for four load levels were performed and S-N-curve for the virgin material was derived. In the next step, again fatigue tension-tension tests were performed but the maximum load was reduced to 20% of static strength and the material tested up to 1.2E6 cycles, to simulate one life cycle. After the long life fatigue tests the specimen were refurbished. The process was defined by using a heated press. The specimen were placed in a tool to keep the shape and then temperature and pressure were applied on the specimen, to melt the plastic and close possible delamination or micro cracks in the matrix material. The refurbished specimens were again fatigue tested on the same stress levels which were applied to the virgin material. It could be shown that a refurbishment of long life fatigue material and an evaluation of an S-N-curve for refurbished material is possible. Especially for high cycle fatigue, the S-N-curves are in a close range so that the use of refurbished material seems possible.