PSI - Issue 28

M.Z. Sadeghi et al. / Procedia Structural Integrity 28 (2020) 1601–1620 M.Z. Sadeghi et al./ Structural Integrity Procedia 00 (2019) 000–000

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In the case of the cohesive element approach, adhesive behaviour was modelled by means a single row of COHD24 elements and for cohesive surface approach, it was modelled as surface interaction property. The joints were clamped on one side and subjected to a displacement control of 1 mm on the other side to simulate real boundary conditions. The meshed model is as shown in Fig. 9 and the properties considered in Table 1.

Cohesive element

Cohesive surface

Fig. 9. FE meshing (top) and boundary conditions (bottom) used in Abaqus.

In our previous study (Sadeghi et al., 2020), a comparison between Maximum nominal (MAXS) and Quadratic traction (QUADS) laws was presented. However, for a ductile adhesive such as Araldite 2015, Quadratic traction laws depicted a better a fit. This could be attributed to the damage initiation envelope of MAXS depicting a Rankine yield surface which is more suitable for brittle materials. In the case of QUADS, this surface depicts the Von Mises yield surface which is particularly used for ductile materials where the failure is through shear. Since Araldite 2015 is moderately ductile, the shape of CZM law plays a significant role in the prediction of P m . Based on the study (Campilho et al., 2013), Trapezoidal and triangular CZM are found to be most appropriate with the former being more accurate. Since for the considered overlap length in this model (L o = 20mm), the results depict an underpredicting of P m of less than 5%, triangular CZM was considered. BK law-based damage evolution is considered over the Power law-based which is discussed in the below section. The fracture toughness (G c ) as a function of mode mix ratio is determined from the mixed-mode characterization tests based on J-integral and ECLM data reduction techniques.

Table 1. Material properties of Araldite 2015. Property

Value

Young modulus (MPa)

1850

poisson’s ratio

0.33

Tensile failure strength (MPa) (t n 0 )

21.63*

Shear failure strength (MPa) (t s 0 )

17.9*

*reference (Campilho et al., 2013)