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Today adhesive technology is of particular importance in different industrial sectors, for example in automotive industry or in aerospace technology [1]. In building industry adhesive technology is often used to avoid punctual transmissions of power. Glued glass elements in constructional engineering are only one example of application. However, the adhesive joint is subject of an ageing process affecting the quality and the durability of the adhesive joint. Therefore, an appropriate monitoring is essential in respect of adhesive joints. Micro wire sensors are miniaturized magnetic contactless sensors of physical quantities [2,3]. Micro wires are made of metallic alloy core and glass coating. Their size, high added value, robustness, simple production process and also their symmetry, glass-coating, possibility of contactless sensing leads to their utilization as a miniaturized sensor with a wide range of applications. Continuous monitoring that provides accurate data not only helps with identification of real-time material properties but also contributes to maintenance planning and reducing risk of future disasters. [3] The most important thing is that micro wires can provide measurements from inside of adhesive bond.
This work provides an analysis of the measurement of a bonded joint subjected to tensile loading. The investigation utilized an aluminum strip of EN AW 6060 as the test sample. The bonded joint was engineered with an overlap area measuring 20$\times$50 mm. Within this bonded interface, a 30 mm micro wire was embedded to facilitate the local monitoring of stress development within the adhesive layer. Two commercially available adhesives were employed for this study: Alteco Super Glue and Loctite Super Bond Power Gel.
The samples were subjected to tensile testing. During the testing, the magnetic response of the embedded micro wires was measured in relation to the applied tensile load. The experimental data revealed that high-quality bonded joints produce a monotonic magnetic response, indicating consistent stress distribution and adhesion integrity. In contrast, low-quality bonded joints exhibited a discontinuous magnetic response, which signifies irregular stress distribution and potential adhesion failures.
The results show that the magnetic microwires could be an effective tool for detecting the formation of defects within bonded joints. By identifying these defects early, it is possible to predict the subsequent failure of the joint. This methodology provides valuable insights into the reliability and durability of adhesive bonds, contributing to improved quality control in manufacturing processes involving bonded joints.
Acknowledgements
This work was partially supported by Slovak Grant Agencies VEGA 1/0180/23 and APVV-16-0079.
References
[1] S. Böhm, H. Thiede, T. Ummenhofer and E. Stammen, “ Damage detection and monitoring of glued elements in civil structures using adhesive layer integrated markers,” https://data.smar-conferences.org/SMAR_2011_Proceedings/papers/110.pdf
[2] A. Allue et al., “Smart composites with embedded magnetic microwire inclusions allowing non-contact stresses and temperature monitoring,“ Composites Part A: Applied Science and Manufacturing, Vol. 120, 2019, pp 12-20. doi: 10.1016/j.compositesa.2019.02.014.
[3] R. Jurc et al., “Sensoric application of glass-coated magnetic microwires in Magnetic Nano- and Microwires, Design, Synthesis, Properties and Applications.“ Woodhead Publishing Series in Electronic and Optical Materials 2020, Pages 833-868 doi: 10.1016/B978-0-08-102832-2.00028-1.
