Effects of embedded SHM sensors on the structural integrity of glass fiber/epoxy laminates under in-plane loads

This experimental research is focused on examining the effects of stress concentration due to the embedded Structural Health Monitoring (SHM) sensors on the structural integrity of glass fiber/epoxy laminates subjected to in-plane tensile loads. Recent advances of health monitoring technologies have resulted in development of micro-dimensional sensors that can be embedded into composite laminates. Notwithstanding their small sizes, such inclusions may affect the response of the composite. Damage induced by the peak values of stress concentration around the embedded devices is, in fact, one of the main concerns. To assess this and related issues, we have fabricated a series of samples with and without embedded (dummy) sensors and micro-processors in S2 glass fiber/epoxy laminates, and systematically tested the samples while continuously monitoring the response by the acoustic emission technique. In this manner we have sought to address the process of damage initiation and evolution within the material. The results show that acoustic events begin earlier on during the loading process, in specimens with embedded sensors and the source of the damage is located near the sensors. These early events are associated with matrix failure at the sensor-resin interfaces through micrographic observations.