OS17-3-3 Investigation of measurement method for damage monitoring of quasi-isotropic graphite/epoxy laminates using ERCM

Abstract

Since damage occurring in laminated composites is usually difficult to detect by means of visual inspection, laminated composites are not reliable enough for primary structures. In order to improve the reliability of laminated composite structures, an in-service automatic system of damage identification is desirable. Todoroki et al. has proposed the damage identification method for graphite/epoxy laminates using the electrical resistance change method (ERCM) and confirmed its applicability for beams and thin plate-type specimens. In this method, multiple electrodes are mounted on the surface of laminates to measure those electrical resistance changes. Damage to the laminate such as delaminations can be detected by measuring the electrical resistance changes caused by damage creation. The ERCM has yet to be investigated for thick laminates, although thick laminates has been used practically in structures such as the primary structure of commercial aircrafts. In this study, in order to evaluate the capability of the ERCM for thick graphite/epoxy laminates, measuring method for the ERCM are analytically investigated with FEM. The delamination is focused as a typical damage of laminated composites. To simulate the actual delamination by FEM, indentation tests and the detailed observations of damage are experimentally performed. In order to improve the detecting capability of ERCM for thick laminates, two kinds of measuring method is compared analytically and its applicability was confirmed.