Self-sensing composites incorporating piezopolymer based acoustic emission sensors

Recent research on thin composite panels has demonstrated the ability to detect and characterise material damage from resultant structure borne stress waves known as Acoustic Emission (AE). The method, involving modal analysis of full AE waveforms, demonstrates a superior means of noise rejection and sourer: location compared to more conventional parameter based AE detection techniques such as amplitude distribution and event counting. This work exploits these advantages for self-sensing composites. An additional important feature in discriminating the nature of material damage mechanisms from their AE signature is the use of a broadband AE sensor so as to minimise signal frequency distortion. As a low-cost alternative to most commercially available high fidelity AE sensors, this work is aimed at investigating the use of flexible piezo-polymer film as a broadband AE transducing element for condition monitoring of composite plates, Preliminary test results are presented from a surface-mounted piezo-polymer transducer for simulated AE sources on a thin composite plate. The results show thai source discrimination and source localisation are feasible in a number of frequency ranges. Attenuation measurements used to establish sensor element spacing are also provided. The next stage of development is to integrate an array of polymer sensors into composite panels to provide an accurate means of damage detection, location and diagnosis of structural integrity.