PSI - Issue 42

Niklas Ladwig et al. / Procedia Structural Integrity 42 (2022) 647–654 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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3.2. Test setup A photography of the MC-DCB test setup is given in figure 3. The tests have been performed in dual-actuator, biaxial servo-hydraulic testing machine (MTS Landmark Bionix, MTS Systems, Eden Prairie, USA). To prevent unintended external loads on the specimen and to avoid lateral forces acting on the actuator, the lower clamping is mounted on floating bearings. In addition, the upper adherend is not fully clamped and allows for a specimen rotation θ as illustrated in figure 1. Consequently, all components of boundary force and moment except the ones shown in the figure 1 are almost zero and can be neglected.

Figure 3 – realised MC-DCB test setup with DIC system

Two six-axis load cells were used to measure the loads acting on the upper and the lower clamping of the specimen. The load cell beneath the lower clamping has a maximum capacity of ± 10 kN for the axial ( y -direction) forces and ± 4 kN for the lateral forces, whereas the capacity for the moments is ± 250 Nm (K6D110, ME Messsysteme GmbH, Henningsdorf, Germany). For SP498, an equal loadcell was used at the upper clamping. For EP4510 a load cell with a capacity of ± 4 kN in axial ( y -direction) and ± 1 kN in the other directions and a moment capacity of ± 100 Nm in all directions was used (K6D110, ME Messsysteme GmbH, Henningsdorf, Germany). An incremental rotary encoder (BDH 1P.05A320000-L0- 5, Baumer AG, Frauenfeld, Switzerland) measured the angle θ at the upper adherend. The lateral displacement u and the rotational displacement α were measured using the integrated measurement system of the testing machine. Additionally, the crack opening displacement (COD) was determined by digital image correlation (DIC) (ARAMIS 3D Motion and Deformation Sensor with evaluation software GOM Correlate, GOM GmbH, Multiple tests with a prescribed constant mixed-mode ratio = . were performed. With the mentioned mixed mode ratio definition, tests between pure mode I ( = 0⁡° ) and mode III ( χ⁡ = ⁡90⁡° ) were performed in increments of Δχ = 5⁡° . The tests were terminated after a visible propagation of the crack by approximately 10 mm, which was the Braunschweig, Germany) with two 12 MP cameras. 3.3. Control on prescribed mode-mixity and test matrix