Detection of Impact Damages in Composite Stiffened Ribs by a PZT Network

In the case study presented, a PZT sensors network has been integrated within several different composite airframes, manufactured from carbon fiber and thermoplastic (PEEK) or thermoset matrix, with integrated omega and T stringers. One of the tested frames is about 400 mm wide and 700 mm high, and integrates 3 vertical hat stiffeners and one horizontal L stringer. The airframe was damaged by impacts with increasing energy levels (from 5 J up to 35 J, by fives) in several locations, by using a standard low energy gravity rig and impactor. BVID levels have been prescribed for each concerned location, so degradation according damage tolerance design allowables must be taken into account. The sensor network is connected to both active and passive systems. Passive monitoring for impact detection basically consists of high frequency signals continuous acquisition during impacts tests over the structure, studying the influence of the damage (delaminations and stiffeners debondings) induced by those depending upon sensor position. Active method, used for damage assessment, requires that at least one PZT works as an actuator, thus generating Lamb elastic waves that propagate along the structure. Damage-wave interaction is studied, in such a way that damage characterization is possible. doi: 10.12783/SHM2015/9