Shearographic Detection of Delaminations in Sandwich Structures: Investigation on Various Excitation Modes

摘要: Delaminations are a common problem that occurs between the core and skins of sandwich structures. Such defects may originate either from malfunctions in manufacturing process leading to reduced adhesion strength or certain types load like impacts during operation. This study was focused on detection such with increasingly popular shearography technique (Butters Leendertz [1]). Shearography is based speckle effect, which when coherent light scattered rough surface. Rays different positions sample surface interfere randomly space create granular kind image, distinct intensity fluctuations called speckles. In shearography, two images same area object simultaneously recorded laterally sheared one another (Fig. 1). Images before after excitation their difference results fringe pattern, associated full strain field.