Onset of Resin Micro-Cracks in Unidirectional Glass Fiber Laminates with Integrated SHM Sensors: Experimental Results

This article presents the results of experiments conducted in order to identify and locate the failure initiation in glass fiber/epoxy laminates with integrated structural health monitoring sensors (SHM) and electronics. Recent advances in health monitoring technologies have resulted in the development of micro-dimensional devices that can be embedded into composite laminates. Notwithstanding their small size, such inclusions may affect the response of the composite. Damage induced by the peak values of stress concentration around the embedded inclusion is, in fact, one of the main concerns in smart structures technology. To address this specific issue, unidirectional S2 glass fiber/epoxy laminated composites are fabricated with embedded small implants that mimic potential sensors and microprocessors. Quasi-static tensile tests are then performed on those samples while monitoring them by the acoustic emission (AE) technique. Additionally, the microstructure of the material with and without implants is explored. The AE results show that early low-medium amplitude events are detected at the implant location and the micrographic inspections reveal that micro-cracks initiate at the device-composite matrix interface and grow around the implant causing the debond of the external component from the surrounding resin system.