Identification of damage location in advanced grid structures using fiber Bragg grating sensor

Abstract

Grid structures are the structures made of the trusses consisting of simple ribs. Especially, the structure which uses carbon fiber reinforced plastic (CFRP) unidirectional composites as ribs is called advanced grid structures (AGS). Highly Reliable Advanced Grid Structure (HRAGS) is one of the AGS in which fiber Bragg grating (FBG) sensors are embedded in the longitudinal direction of the ribs in order to detect various damages that appear in the composite grid structures. In this research, the authors tried to identify the damage location in AGS from the structural strain distribution measured by FBG sensors embedded in all ribs. When some damages appear in the AGS, the structural strain distribution in the AGS changes accordingly. Considering the tendency of change, the damage location was identified. At first, FBG sensors were embedded into AGS and three point bending test was examined. The result showed that these embedded sensors could detect the strains applied to the corresponding ribs. Then, low velocity impact test was carried out, which revealed that only fiber breakage was appeared in the AGS. Moreover, three types of models for finite element analysis (FEA) were proposed and compared with the experimental result. According to the comparison, the authors selected beam element model (BEM) for damage-location identification in this research. Furthermore, strain distributions in the structure including damages were calculated with this model. The result proved that the identification of damage location could be realized.