Strain Transfer Characteristic of FBG Sensor Attached on the Composite Laminates under Different Installing Angles

Composite materials such as carbon fiber reinforced polymer (CFRP) have received widespread attention because of their extraordinary mechanical properties. The application of CFRP laminates in lieu of traditional metal alloys has significantly increased in aircrafts. Fiber Bragg grating (FBG) sensors are widely used in strain measurement of composite materials. However, for the strain measurement with FBG sensors, it is usually assumed that the strain measurement accuracy is not influenced by the installation direction of the FBG sensor, which introduces measurement errors for composite laminates. In this paper, a strain transfer model is proposed to evaluate the strain transfer ratio from anisotropic CFRP laminates to surface-attached FBG sensor under different installing angles, and the characters of composite laminates that influence the strain transfer efficiency are analyzed. According to the experimental results, the maximum strain measurement error for composite laminates is only 0.242% by compensating the measurement error caused by installation directions of FBG sensors.