Feasibility of Embedded Distributed Optical Fibre Sensors in Thermoplastic Composite Braided Beam Structure

In this paper, consolidation monitoring and structural health monitoring (SHM) of a braided thermoplastic composite beam was performed using a distributed optical fibre sensor (DOFS). The DOFS was manually embedded into the braided preform before melt processing. The real-time strain and temperature data obtained during consolidation and cooling segments were correlated with phase transitions in the thermoplastic matrix. Post consolidation, the quality of the embedded DOFS was investigated using a micro-CT to reveal defects such as waviness and misorientation due to the crude nature of the adopted embedding technique. The manufactured beam was then subjected to repeated loading-unloading cycles in a flexure test. The strain developments along the embedded optical fibre length were comparable with the measurements from Digital Image Correlation (DIC), and further correlated with the post damage observations. Despite the crude method of embedding the optical fibre, the monitored data was useful for consolidation monitoring as well as SHM. This proved that DOFS could be embedded into composite structures without adding cost, time and complexity thus making them feasible for industrial applications.