Monitoring the Hydrolytic Degradation of Polyester-Based Composites by a Piezoelectric Method

Abstract

Theoretical considerations show that the electric impedance of a piezoelectric element depends on the physical and geometrical properties of the element and also on the viscoelastic characteristics of the different media surrounding it. According to a dynamic model, an original technique has been developed by inserting a piezoelectric ceramic in the composite structure when processed. The electric signal, after signal processing and numerical treatments, gives access to the viscoelastic properties of the external medium. This method is an excellent indicator to display the polymerization kinetics of the resin as well as the post-curing phase of the composite structure process. Moreover, a further application of this nondestructive method is the monitoring of the hydrolitic degradation of the composite structure. The evolution of the electric impedance of the piezoelectric sensor is presented here as a function of water exposition time for a polyester-based composite.