Local Strain Monitoring of Fiber Reinforced Composites under High Strain Fatigue using Embedded FBG Sensors

This work studies the strain monitoring of biaxial glass fiber reinforced epoxy matrix composites under a constant, high strain uniaxial fatigue loading using embedded Fiber Bragg Grating (FBG) optical sensors. Three consecutive FBG sensors written on a same fiber optic cable were embedded within the composite specimen along the gage length to study the distribution and evolution of local strains during the cyclic loading. Results show that local strains measured by FBG sensors under the global constant strain can experience considerable variations as the loading progress demonstrating the effect of local damage on the local strains. Autogeneous heating along the specimens were also monitored using thermocouples mounted on the location of the FBG sensors to investigate the effect of temperature variations on FBG measured strains and damage formation.