Obtaining traction-separation laws of adhesive joints using optical fiber strain measurements - Part A (Mode I)

This work presents a new method for obtaining traction-separation laws (TSLs) from double cantilever beam (DCB) tests in mode I of adhesively bonded joints. Thereby a structural adhesive was used. The focus is on the applicability of an optical fiber sensor using beam theory and its comparison with more or less conventional methods. The optical fiber, attached along the length of the sample, allows real-time measurement of strain with high spatial resolution on the adherent throughout the test. This newly introduced technique provides information on crack-tip position and traction-separation relationships in the context of cohesive zone modeling (CZM). These data have been shown to provide rich evaluation possibilities. Additional measurements with force and position sensors, as well as rotary encoders, support the determination of the J-integral. With the help of these measurements, a good amount of information is available to apply various methods to evaluate a single experiment. Geisel and Marzi (2024) were also able to show in part B of this paper that this method can also be applied to mode III and achieved comparably good results.