Damage Monitoring for Semi-Transparent Composites Using Luminance of EL Backlight

Abstract

The present paper a new damage monitoring system that employs luminance of EL backlight for semi-transparent composites. For the semi-transparent composites, damage is easily found by visual inspections. In the cases that the structures are sealed or huge structures, however, the visual inspections are difficult. The present paper adopts a system using change of luminance of transmitted light. When the composite structures are damaged, the damage reduces luminance of the transmitted light from the backside. The present study adopts an Electro Luminescent device (EL) as the backlight. The EL device can emit uniform-plane-light and is a very flexible device. The EL device can be mounted on a curved surface. Fatigue tests are conducted using rectangular specimens with an open hole fabricated from fabric glass/epoxy composites. The monitoring system is applied to the fatigue tests, and it is experimentally shown that the method can detect the fatigue damage without loading.