Fiber Bragg Grating High Impact Force Sensors With Adjustable Sensitivity and Dynamic Range

This paper presents the development of a fiber Bragg grating sensor system for loads applied perpendicularly to the fiber axis. The sensor design allows for adjustable sensitivity and high impact resistance. Two designs were tested, each containing a fiber Bragg grating embedded in a polymer material and encased in aluminum. Testing with a rate controlled load press was used to show the dependence of the response on loading conditions with loads reaching kN levels. Projectile drop tests further showed the response of both types of sensors with forces applied over millisecond durations. The magnitudes of the measured wavelength shift loading and unloading rates ranged from 0.203 to 0.507 nm/ms. Static structural simulations were completed and are in agreement with the experimental results. Loading rates of 1.667 mm/s with contact areas ranging from 38.5 to 113 mm
²
resulted in respective sensitivities ranging from 0.154 to 0.064 nm/kN. Simulations and experiments further demonstrated the ability to increase the sensitivity up to 99% through modifications of lid thickness, cavity diameter, and loading area.