A modified single-leg bending test to study mode III fracture of adhesive joints

The mode-III fracture behavior of structural adhesive joints is examined using a modification of the SLB specimen. Tests were performed on the adhesive SikaPower®-498. Crack growth resistance curves and traction separation laws in the context of cohesive zone modeling were obtained from the experimental data. Finally, data reduction schemes based on both simple beam theory and the J-integral are applied and discussed. To measure the crack-tip position (which cannot be easily detected with a simple camera since no practical line of sight exists in this particular test setup), both a digital image correlation (DIC) system and fiber-optic strain measurements were utilized for an indirect determination of the crack-tip position. Both systems allow multiple ways to evaluate the measured data, hence giving rise to a few different methods to locate the crack tip which were analyzed and compared regarding their benefits and disadvantages.