SHERLOC: Innovative Manufacturing and Structural Health Monitoring of Thermoplastic Structures

SHERLOC project is a European project framed within CleanSky research programme funded by the EU's Horizon 2020 programme. SHERLOC tries to respond the industrial needs regarding the structural health monitoring of real new generation aerospace structures. The project looks for the manufacturing of innovative aerostructures and structural health monitoring techniques which allow the detection of possible issues on the structures during in-service, such as impacts or strikes. A Carbon Fiber Reinforced Thermoplastic (CFRTP) window frame demonstrator was manufactured using woven CF/PEEK material supplied by Toho-Tenax. The selected manufacturing process was press-forming in a hot-press. Thermoplastic composites have been under the spotlight of the aerospace industry for decades due to the many advantages that may offer, such as recyclability, good mechanical performance and the opportunity of new out-of-autoclave manufacturing processes. To evaluate the quality of the thermoplastic window frame, some physical-chemical and mechanical testing were performed, including void content analysis, differential scanning calorimetry (DSC) and plain-compression testing. In addition to that, ultrasonic non-destructive inspection (NDI) was performed to evaluate the quality of the manufacturing process. In addition of innovative thermoplastic structures, aerospace industry has been investing in Structural Health Monitoring (SHM) technologies for many years to come to an industrial solution. Thus, a strategy was defined to monitor damages on thermoplastic structures, by combining elastic waves propagated through the structure, using piezoelectric (PZT) sensors. SHERLOC project will assess piezoelectric (PZT), fiber optic (FO) and hybrid (PZT-FO) based techniques to perform the SHM of aeronautical structures. The scope of this paper is the evaluation of the piezoelectric based techniques when applied to the monitoring of the thermoplastic window frame.