Fatigue Life Measuring System Using Fiber Optic Sensors for CFRP Pantograph Upper Arm

A life assessment method based on fiber Bragg grating (FBG) sensors is investigated for carbon fiber-reinforced plastic (CFRP) upper frames that are subjected to cyclic loading and are prone to fatigue damage and shortened fatigue life. Based on the research of optical fiber sensing technology, a measuring system for the fatigue life monitoring of the upper arm on the carbon fiber composite pantograph is developed and evaluated in this article. The sensing principle of the optical fiber grating sensor and the construction and installation of the sensing network is described in detail. A carbon fiber composite upper frame fatigue monitoring platform is designed for systematic testing, and life is assessed through measured point strain average and strain amplitude combined with a fatigue cumulative damage model. The effectiveness of the designed system is verified by analyzing and comparing the fatigue simulation results of the carbon fiber composite upper arm with the measured data of the sensor installed on the fatigue life test platform of the upper arm. Experimental results show that the system designed by optical fiber sensing technology is capable of accurately detecting the fatigue life of the upper arm of the carbon fiber composite, which can be used for real-time detection of the fatigue life of the upper arm by analyzing the characteristic parameters of the upper arm of the carbon fiber composite.