Low Coherence Speckle Interferometry (LCSI) for the characterisation of adhesive bonded joints

Low Coherence Speckle Interferometry (LCSI) combines depth-resolved measurements of Low Coherence Interferometry and high-accuracy deformation measurements of Electronic Speckle Pattern Interferometry. Depth-resolved deformation measurements enable e.g. the characterisation of the behaviour of interfaces in transparent and semi-transparent materials. In this work theoretical background and basic principles of LCSI are described. The setup and the measurement algorithms are optimised. The contrast of the interference signal depends on the configuration of the optical setup and the optical properties of the material. Theoretical investigations and measurements for optimising the beam ratio, the coherence function and imaging parameters are presented. LCSI is introduced as a tool for characterisation of adhesion. Fundamental studies on interfacial instabilities in adhesive bonded aluminium joints are carried out. To quantify the measurement results an one-dimensional model is developed.