Measurements of Temperature and Residual Strain during Fatigue of a CFRP Composite Using FBG Sensors

Fatigue behaviour is a major point for structural materials. In this paper temperature and residual strain during fatigue of a carbon fiber reinforced polymer (CFRP) are measured. CFRP beam specimens, with fiber Bragg grating (FBG) sensors and thermocouples embedded at selected locations, are subjected to three-point bending cyclic loading at 0.1 Hz, 1 Hz, 10 Hz and 20 Hz. Thermocouples are used to measure the temperature while FBGs can sense the temperature and strain as well. From the experimental results, transient steep peaks of temperature increases (up to 2.3degC) are discovered at the beginning of loading. The temperature increments due to fatigue are around 1.0degC, which are not relevant to frequencies from 0.1 Hz to 20 Hz. The residual strains of 10 muepsiv-20 muepsiv during fatigue are reported, independent of loading frequency and FBG location.