Non-Destructive Testing of Hollow Sphere Sandwich Plates Using Guided Waves

Abstract

Online damage detection in thin wall light weight structures with guided waves is one common way to develop structural health monitoring (SHM) systems. To understand the behavior of wave propagation typically homogeneous plates made of aluminum and composite reinforced plastics (CFRP) are studied. However, hollow sphere sandwich plates among the cellular materials, have a high potential for the design of light weight structures. Therefore, the potential of elastic guided waves for damage detection in these materials has also to be investigated. In this work the wave propagation in an hollow sphere sandwich plate is studied with 3D laser scanning vibrometry. Two guided wave modes are excited with an applied piezoceramic patch actuator. These modes are found traveling through the top and bottom plate, and interactions with discontinuities have been found. Utilizing a computer tomography (CT) the inner structural discontinuities are visualized and debondings between the core material and the cover plates are found. In the paper the experimental results are presented and it is shown that the measured wave field can be used to detect damages inside the structure of a sandwich plate.