The use of optical fibers for fatigue testing of fiber-reinforced thermoplastics

This study investigates the possibility of using optical fibers with Bragg gratings for measurements under fatigue loading conditions. Detailed information is given on the principle of optical fiber measurements, the embedding process and the fatigue tests. To verify the strain derived from the optical fiber, the strain is compared with extensometer measurements. Furthermore, X-ray micro-tomography is discussed and used for the visualisation of the optical fibers and damage in the composite material. The material used for this study was a carbon fiber-reinforced polyphenylene sulphide. It can be concluded that the optical fiber survives over half a million loading cycles, without de-bonding of the fiber. Furthermore, the resolution of the micro-tomography is high enough to visualise not only the optical fiber, but also damage in the material