PSI - Issue 68

Lukas Dominik Geisel et al. / Procedia Structural Integrity 68 (2025) 1273–1279 L. D. Geisel and S. Marzi / Structural Integrity Procedia 00 (2024) 000–000

1277

5

Process zone

Long beam

6000

Short beam

5000

4000

3000

Backface strain /

2000

1000

0

350

400

450

500

550

600

Position

/ mm

x

Fig. 3: Singular backface strain measurement with depicted process zone

22.5

50

20.0

40

17.5

/ kJ/m²

15.0

/ MPa

OFS

coh

30

7.5 Energy release rate J 10.0 12.5

20

Cohesive traction

5.0

10

2.5

0.0

0

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Crack opening displacement w

Crack opening displacement w

/ mm

/ mm

COD

COD

(a) Typical curve of a singular ERR measurement plotted over the respective COD

(b) Typical resulting traction-separation law

Fig. 4: Typical measurements of the ERR, the COD and the TSL

Using the new method, larger final CODs are measured and the decline of the cohesive stresses is more gradual once damaging of the adhesive starts. To check the consistency of the new method between di ff erent test specimens, the maximum values of the cohesive traction and the COD at complete failure are compared in Fig. 7. The latter was determined using the COD at which τ coh ( w COD ) fell under five percent of τ coh , max .

5. Summary

It can be summarized, that a large amount of cohesive laws can be obtained with the newly proposed evaluation method whilst only needing a few conducted tests. The obtained laws are mostly consistent with previous results indicating the applicability of the proposed evaluation method for the investigation of the fracture behaviour of structural adhesive bonds. One benefit lies in the usability of this method with test setups, in which the classical measurement methods are not easily achievable due to di ffi culties in the measurement of the required angles and / or the CTOD. However, these benefits come at the cost of a relatively expensive measurement system that is required to measure strains using glass fibers.