Real-time monitoring of thermal history of thermoplastic automatic lamination with FBG sensors and process modelling validation

Abstract Automated fibre placement (AFP) of thermoplastic composites has been reaching a high efficient and technological level in the last years. In situ consolidation (ISC) process involves cost reduction since extra autoclave cycle is not required. A good control of the temperature and pressure during the lamination is mandatory to achieve a good consolidation without thermal degradation for the manufacturing of high quality parts. Due to the manufacturing set-up, temperature monitoring is limited to infrared thermographic cameras and superficial measurements. Within this context, Fibre Bragg grating (FBG) sensors emerged as a potential device for thermal history monitoring in real-time. An investigation was carried out by using different FBG sensors for process monitoring of thermoplastic ISC. In this study, the sensors were embedded inside CF/PEEK thermoplastic samples and the lamination process was subsequently monitored. Also, a thermal model was created in order to obtain a simulated thermal history of the process. The process was successfully monitored, and it has been demonstrated that FBG sensors are a useful tool for thermoplastic ISC process monitoring. The results provided by the sensors allowed to identify different phases of the process (heating, consolidation and cooling down). The thermal history of the process was monitored by encapsulated FBG sensors acting as temperature probes. A good correlation between the sensors and the thermal was found. In addition to that, First steps were taken for strain history monitoring by means of FBG sensors.