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. Experimental 3.1. Specimen preparation

Figure 2 - Specimen in unloaded state (dimensions in mm)

For the experimental investigation, two different epoxy-based adhesives were chosen. While Henkel Teroson® EP4510GB, (EP4510) behaves rather brittle, SikaPower®-498 (SP498) is an elastic-plastic crash-optimized adhesive. The dimensions of the MC-DCB specimen are given figure 2. In order to avoid plastic deformation of the adherends during testing, the width of the adhesive layer was chosen to be smaller than the width of the adherends. To simplify specimen manufacture and the clamping, a notch has been milled into the adherends which leads to the depicted shape of adherends. The chosen total lengths and the initial crack (lever arm) lengths of the specimens differ between both adhesives. For EP4510, = 250⁡mm and 0 = 120⁡mm have been chosen, for SP498 = 500 mm and 0 = 80⁡mm , respectively. For both adhesives the nominal adhesive layer thickness was 0.3 mm. Before applying the adhesives, the adherends were sandblasted with corundium and rinsed with Butanone to eliminate contaminants on the bonding surfaces. PTFE tapes were placed at the beginning and the end of the adhesive layer, to ensure a constant adhesive layer thickness. The adhesive, preheated to 50 °C, was applied to the likewise preheated adherends. During curing, at 175 °C for 25 min, the adherends were held in place with screw clamps. After removing the PTFE tapes, the greyscale speckle-pattern was applied with a black lacquer coating and a white speckle pattern. All specimens were then stored a maximum of five days under laboratory conditions prior to testing.