Use of infrared thermography to investigate the fatigue behavior of a carbon fiber reinforced polymer composite

Thermography was used to investigate the fatigue behavior of a braided carbon fiber polymeric composite plate. A thermographic approach, originally developed in an earlier study for metallic alloys, was employed to rapidly determine the composite high cycle fatigue strength. The method yielded a fatigue threshold value that was in excellent agreement with that obtained through a conventional experimental test program. The damage mechanisms responsible for the increased heat dissipation and ultimately failure were identified, which provides support for the existence of a fatigue threshold for this material. An extension of the thermographic technique to rapidly determine the entire fatigue stress-life curve for the composite plate provided a direct correlation to the stress-life curve determined through a conventional test program. Energy dissipation was also used as an indicator to determine the high cycle fatigue strength, providing support for the thermographic approach. A relationship between the dissipated heat, the intrinsic energy dissipation and the number of cycles to failure has been clearly established.