Damage monitoring of glass/epoxy laminates with luminance of backlight of EL device

Authors have proposed a new damage monitoring system that employs luminance of EL backlight for transparent composites such as glass/epoxy composites. For the 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 to perform. ne 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. In the present study, the method is applied to the glass/epoxy and Al2O3/epoxy composites fabricated from the unidirectional glass/epoxy prepreg. For these non-fabric composites, the silhouette of the matrix cracks is quite, different from the damage silhouette of the fabric composites. In the present study, therefore, the method is applied to the unidirectional composites: glass/epoxy and Al2O3/epoxy composites. Specimens were made from the cross-ply laminates. Tensile tests are conducted using rectangular specimens with open holes fabricated from cross-ply glass/epoxy and Al2O3/epoxy composites. 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 without loading with measurements of the luminance of transmitted light of the EL device.