Slow and fast dynamics to control damage in heterogeneous materials: application to concrete and glass/fibre polymer

Abstract

The monitoring of the nonlinear acoustic properties of high performance structural materials during damaging mechanical tests is presented. The samples were instrumented using piezoelectric sensors, which were hardly glued to the surface of the samples constituting a smart structure allowing the in situ health monitoring of the material. Fast dynamics experiments have allowed the monitoring of damage through the changes of the frequency and the quality factor under the effect of the excitation amplitude. With the help of slow dynamics we used the relaxation time as a damage indicator and could differentiate damaged and undamaged concrete samples. After that, we used slow dynamics relaxation time as a tool to monitor the damage induced gradually with three points bending tests in a polymer composite sample. Slow dynamics, which is a new and very sensitive damage indicator, is qualified for future applications in health monitoring of smart or instrumented structures.