The growing demand in lighter and safer structures generates the requirement of lighter joining strategies, particularly for lightweight metal alloys, composites, and also joining dissimilar materials together. Titanium alloys stand out as the conventional choice for materials for light weight structures. Adhesive bonding of titanium is an appealing route for joint design, also for the possibility of joining it with dissimilar materials. The realization of a strong joint depends not only on the joint design and type of adhesive, but also on the preparation of the adhering surface. Laser texturing presents advantages compared to common surface preparation processes in terms of eco-compatibility, energetic efficiency, ease of manufacturing, and repeatability. This work presents a preliminary investigation on laser texturing of Ti6Al4 V alloy with a pulsed fiber laser source with the aim to increase surface adhesion for bonding. Particularly, different surface textures are proposed, and laser machining strategies are developed. The results showed that laser texturing provided up to eightfold and 30% higher shear strength compared to plain and sand blasted surfaces, respectively. Failure analysis showed that a margin of improvement is still possible by adapting the surface texture for better cavity filling and reducing surface damage caused by the laser treatment.

In this work, a method for monitoring fatigue crack growth in a metal to composite bonded joint based on the strain field is proposed and applied in the framework of a visualization tool based on Augmented Reality (AR). This tool superimposes some virtual objects, which are the data acquired by the sensors and the crack length, directly on top of the specimen under inspection and in real time. By finite element (FE) analyses, a good correlation between the crack tip position and the strain field in a single lap specimen is found and this feature is exploited to monitor the crack length during fatigue tests and to feed the AR system to virtually visualize the crack on the real specimen. An array of electrical resistance strain gauges is bonded to the surface of one adherend. A Matlab function collects values from the strain gauges mounted on the specimen under investigation analyses them on the basis of the FE analysis and finally feeds the AR system. The validation of this process is done by measuring the crack by optical microscope. This procedure is also tested with the use of Fiber Bragg Gratings (FBG) optical strain gauges

In this paper, a framework based on Augmented Reality (AR) and a mobile device is proposed for monitoring mechanical components during fatigue tests. This solution enables the user to move around and to inspect the component through AR from different points of view. In addition, the framework proposes a solution to estimate in real time the crack growth and to visualize it directly onto the component. A user application is developed according to the proposed framework and it is used for case studies of fatigue test for adhesively bonded joints.