Structural Health Monitoring of a Carbon Fibre Structure using low profile piezoelectric, optical and MEMS sensors

As part of a recently completed part-funded DTI/MOD programme entitled "DECODA", trials were carried out to monitor a 110 by 65 cm curved Carbon Fibre Reinforced Composite (CFRC) structure during impact and fatigue trials. Three types of sensors were used to detect Acoustic Emissions (AE) emitted from the panel, namely optical fibre cavity sensors, micro-machined ultrasonic MEMS (Micro-Electro-Magnetic-Systems) sensors and low profile piezoelectric ceramic sensors. Information from these sensors were then used to provide information on the extent and location of any AE source and compared with the response of commercially available piezoelectric transducers (WDI- Physical Acoustics ltd.). The results indicated that all three technologies were capable of detecting AE generated both from the impact and subsequent loading of the structure. The project also demonstrated a Digital Signal Processing (DSP) system built to record and out-put test data from any of the sensors. During the trials a direct comparison was made between the low profile piezoelectric ceramic and WDI sensors. From this data it was demonstrated that the low profile piezoelectric ceramic sensors could detect and locate a significant proportion (up to 95%) of the total AE events recorded. It was shown that the majority of the AE events correlated with the site of impact and delamination damage was confirmed from C-scans of the panel. This paper describes the test matrix used and summarises the results of the trials.