Life cycle monitoring and advanced quality assurance of L-shaped composite corner part using embedded fiber-optic sensor

L-shaped composite parts are structural key elements in complex-shaped aerospace composite structures, and life cycle cross-sectional strain change is their key. This study developed a fiber-optic-based life cycle monitoring system for L-shaped corner parts. A fiber Bragg grating (FBG) sensor was embedded in the through-thickness center of a corner part and the cross-sectional strain change was continuously evaluated by using a birefringence effect of the FBG. The embedded sensor could capture key strain changes throughout the structural life cycle, confirming that “non-axisymmetric strain” of the FBG sensor is a good indicator for spring-in distortion in manufacturing and through-thickness tensile failure in operation. The developed system was further utilized for advanced quality assurance of assembled L-shaped parts, and a new strength prediction method was proposed based on the FBG response. The monitoring system developed can provide a deep insight about the current internal state of L-shaped parts, and the information obtained is highly valuable for improving the design/manufacturing and for diagnosing the structural health.