A procedure to embed fibre Bragg grating strain sensors into GFRP sandwich structures

Embedding FBG strain sensors within a GFRP sandwich composite material allows early detection of internal defects. However, the sensors need to survive the manufacturing process to provide this capability. Vacuum infusion is commonly used to manufacture GFRP sandwich composite materials but, it needs to be modified to accommodate the embedding process. A stage by stage procedure is demonstrated here to embed FBG strain sensors between the skin–core interface of a GFRP sandwich beam specimen using the vacuum infusion method. Practical issues relating to sensor placement, fibre alignment, specimen lay-up and resin infusion are discussed. Also, the post cure effects of the resin on the FBG strain sensors are investigated. Static and dynamic load analyses are then performed to verify the repeatability and accuracy of the FBG strain sensors.