Comprehensive Investigation of Static and Fatigue Performance of Fiber Bragg Grating, Digital Image Correlation and Strain Gages

In contemporary practice, a significant application of strain gauges lies in the experimental stress analysis of structural components, particularly within the aerospace sector. However, over the last two decades, fiber optic sensors, particularly Fiber Bragg Grating (FBG) sensors, have been successfully utilized for strain measurements, gaining recognition for their dependable performance. These sensors deliver strain measurement precision that rivals traditional methods such as strain gauges and extensometers. A major advantage of FBG sensors over electrical strain gauges lies in their long-term stability. Additionally, FBG sensors support multiplexing, meaning several sensors can be placed on a single fiber, enabling the collection of multiple simultaneous measurements including the detection of strain, pressure, temperature, and vibration signals. Nevertheless, FBG and conventional techniques also exhibit similar features: they provide localized, directional measurements, require temperature compensation, and are often applied by bonding them to the surface of structures. Digital Image Correlation (DIC), on the other hand, is a non-contact optical method that measures full-field surface geometry, displacement, and strain using digital cameras. DIC is especially useful for monitoring structures by taking periodic images and determining strain and displacement over time or under various operating conditions. While traditional tools such as resistive strain gauges are frequently used in testing composite materials, they come with certain challenges. These include bonding and surface preparation difficulties, the need for direct surface contact and providing only single-point data. While DIC provides a broader measurement capability, its precision depends heavily on the quality of the calibration process and the testing conditions. This study investigates the experimental assessment of strain through the application of traditional strain gauges, FBG sensors, and DIC methodologies on glass fiber reinforced composite (GFRC) laminate coupon specimens subjected to quasi-static and constant amplitude fatigue loading. The work aims to comparatively investigate the sensitivity of optical fiber sensors, strain gauges and DIC.