DGZfP Proceedings BB 90-CD

Active Fiber Composites (AFC) manufactured at EMPA with commercially available piezoelectric ceramic fibers have been investigated for their potential use as Acoustic Emission (AE) sensors. AFC elements have been evaluated with methods derived from AE sensor characterization as well as additional measurements. Some commercial AE sensor types have been evaluated with the same methods for comparison. For both, AE sensors and AFC elements, sensitivity versus frequency and electrical impedance versus frequency measurements yield indications of the respective resonance frequencies of the piezoelectric sensor. Simulated AE applied on test plates shows an additional anisotropy of the sensitivity of the AFC for AE signals arriving from different directions relative to the fiber orientation. This anisotropy of the sensitivity of the AFC elements can, in principle, be applied to enhance the sensitivity of the AFC elements along certain fiber orientations of the composite structure. Their planar design and lower mass, combined with their intrinsic conformability make AFC elements seem well suited for structural integrity monitoring applications.