Material elastic waves test exploitation in benefit of composite structure health monitoring

Abstract

Composite structures suffer from an unsatisfactory behavior to impact damage, which involves conservative designs, high maintenance and repair costs in order to prevent premature failures. These time-consuming operations can be optimized by SHM techniques. In the case study presented, a 48 PZT sensing network has been integrated within two similar composite panels, representative of real aeronautical structures and multi-functional skin concept, approximate size 600mm width and 1650mm length, with substrate made of carbon fiber and thermoset matrix, with two integrated hat stiffeners along the longitudinal direction, and transverse C metallic stiffeners. This sensors network may be used by both active and passive techniques. Passive monitoring consists in the continuous acquisition of high frequency signals during impacts tests on the structure, and thus detecting impact time and location. Active methods require that at least one PZT works as an actuator, thus generating elastic Lamb waves that propagate along the structure. Damage-wave interaction is studied, in such a way that damage detection and location should be possible. The test plan includes different sources of damages from an instrumented impact hammer till air shotgun scenario, taking into consideration BVID levels defined for each part. This paper deals with the analysis of waves traveling through the structure in benefit of event and damage characterization.