Damage Monitoring of Al_2O_3/Epoxy Laminates with Luminance Change of Transmitted Light from EL Device

摘要

Authors have proposed a new damage monitoring system that employs luminance of Electro Luminiscent (EL) backlight for transparent composites such as glass/ epoxy composites. For the transparent composites, damage is easily found by visual inspections. In cases where the structures are sealed or are large structures, however, the visual inspections are difficult to perform. The present paper describes a system using 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 uses an EL device as the backlight. For Al_2O_3/epoxy composites, the transparency itself is quite different from that of glass/ epoxy. The damage silhouette is also quite different from that of glass/epoxy composites. In the present study, therefore, the method is applied on the unidirectional Al_2O_3/epoxy composites made of unidirectional prepreg in order to check the effectiveness of the method. Specimens were made of unidirectional and cross-ply laminates. Tensile tests are conducted using rectangular specimens with an open hole fabricated from cross-ply and unidirectional Al_2O_3/epoxy. The luminance of the transmitted light of the EL device increases with the increase of the elastic deformation of the transparent composites by tensile loading. The damage is monitored with measurements of the luminance of transmitted light of the EL device.