Thermally induced strain in joints with dissimilar adherends bonded with a flexible adhesive

In this study, assemblies comprising poly(methyl methacrylate) (PMMA) bonded to glass were subjected to a temperature gradient from +30 °C to −40 °C at 0% humidity. Their behaviour was recorded using a 3D digital image correlation (DIC) setup. The deformations and the thermally induced surface strain development, due to thermal loading, were recorded using a stereo camera system with two charge-coupled device (CCD) cameras. Narrow field measurements were performed near the edges of the joint where a high concentration of peeling and shear strains might be expected. With the use of commercial DIC software, the thermal deformation of the structure and the developed surface strain fields (εxx, γxy, εyy) are analysed. Joints with different bond line thickness (0.5 mm, 2 mm, 3.2 mm) of the silicone adhesive were investigated. The continuous image capture with the CCD cameras allowed identification of the failure conditions and the exact moment of failure of the bonded assembly. Additionally, the DIC experiment results were evaluated with the help of finite-element analysis results, which are in excellent agreement. This showed that the DIC method can be successfully applied for the investigation of thermally induced strains in adhesively bonded assemblies and thus contribute to understanding of the underlying thermal/mechanical behaviour of bonded systems.