Impact damage detection system using small-diameter optical-fiber sensors embedded in CFRP laminate structures

The mechanical properties of composites subjected to out-of-plane impact decrease markedly from even barely visible damage. In this study, three damage detection technologies are explained: (1) Technologies for the arrangement of embedded small-diameter optical fibers that have no serious effect on the mechanical properties of composites; (2) Technologies for the egress of the optical fibers using 'the embedded connector for smart structures' that can be trimmed without damaging the optical fibers; and (3) Technologies for a damage detection system that has data acquisition and analysis functions, evaluates the initiation and the position of damage, and visualizes damage information. We conducted an impact test using the composite airframe demonstrator. FBG sensors are embedded in the upper panel of the 1.5 m diameter, 3 m long stiffened cylindrical composite structure for strain measurement, and optical fibers are embedded for optical loss measurement. Damage detection in composite structures using the developed damage detection system was demonstrated.