Characterization of Hybrid-Dissimilar Joints Using Non-Destructive Thermographic Techniques

In recent years, new manufacturing processes and joint techniques have been developed to reduce weight while improving sustainability and circularity in the design of components and structures. In this context, monitoring structures using non-destructive techniques can provide useful information about the presence of defects that can compromise the strength of the material and lead to unexpected early failure. Detecting, quantifying, and then repairing components can extend their life, increasing sustainability. The aim of this work is the non-destructive characterization by means of thermographic techniques of hybrid dissimilar materials made of a layered structure in which the bulk material (additive manufactured AlSi10Mg) is coated with carbon fibre skins. In particular, the presence of detachments between the bulk and coating has been investigated on several specimens classified according to the 3D building direction of the bulk material: 0°, 45°, 90°. Several tests were carried out adopting lock-in and step thermography using two halogen lamps with a total power of 1300 W. Data were analysed with several algorithms and a quantitative evaluation of the damaged area was performed. Moreover, the Thermoelastic Stress Analysis (TSA) has been used as an NDT technique for assessing the damaged area before tensile and bending tests. Finally, possible correlations between mechanical properties and damaged areas have been investigated by using statistical tools.