PSI - Issue 68

D. Linn et al. / Procedia Structural Integrity 68 (2025) 1259–1265 D. Linn, W. Becker / Structural Integrity Procedia 00 (2024) 000–000

1262

4

Fig. 2. Discretisation of the Finite Element Model in Abaqus.

New approach

Δ T = -100 K

FEM

l = 25 mm Aluminum Steel

z x

t 2 = 4 mm t 1 = 1 mm

Fig. 3. Interlaminar stresses along the interface (right) for the configuration of a patch on a substrate under thermal loading (left).

5. Stress analysis

For the situation of a patch on a substrate under a thermal loading, the interlaminar stresses σ z and τ xz along the interface of both layers are now evaluated (see Figure 3, and for material parameters Table 1). The plot shows that the expected stress singularity at the edge is approximated very well and shows an almost perfect agreement with the FEM calculation.

Table 1. Material parameters. Parameter

Aluminum

Steel

Unit

Elastic modulus E Poisson’s ratio ν

70000

210000

MPa

0 . 33 23 . 1

0 . 33 11 . 3

-

6 K − 1

10 −

Thermal expansion coe ffi cient α th

As mentioned before the generic configuration can be used for other load cases as well. Therefor, only the boundary conditions have to be changed. In the following a Double Cantilever Beam and a Single Lap Joint under mechanical loading are considered. The interlaminar stresses are shown in Figure 4 on the left-hand side for the Double Cantilever Beam and on the right-hand side for a Single Lap Joint (see also Table 1 for material parameters). In both cases good agreement between the analytical and the FEM solution can be seen, especially for the Double Cantilever Beam the peel stress σ z shows an almost perfect agreement.

6. Failure prediction - Crack initiation

The failure evaluation as the initiation of a debonding crack is now carried out for the configuration of a patch on a substrate under thermal loading.