Smart layer for damage diagnostics

In this research damage diagnostics is carried out by a novel design of a smart layer that consists of piezoelectric films. This thin layer is attached to the structure being monitored. First, some fundamental investigations are carried out in order to examine the influence of the thickness of the film, the influence of different adhesives, and the influence of the couplant. The wave field generated by the smart layer propagates into a solid. The directional dependency is investigated. Moreover, an improved type of polyvinylidene fluoride (PVDF) copolymer is presented and investigated for the potential application in the field of structural health monitoring. The use of this PVDF copolymer makes the manufacturing process of a self-sensing actuating layer in ultrasonics much easier than conventional PVDF films since the piezoelectric film is directly sputtered onto the surface of a metallic specimen or onto a metallic layer. This smart layer technique is a valuable tool for identifying the location and size of cracks and delaminations in composites as well as for determining local material thicknesses which might occur due to corrosion. It can be applied in order to monitor the so-called 'hot spots' on new structures as well as on already existing structures. The application of the smart layer is demonstrated on a plate-like structure containing a damage. The identified damage corresponds well with the actual damage.