PSI - Issue 19

Christian Schneider et al. / Procedia Structural Integrity 19 (2019) 370–379 Ch. Schneider, et al/ Structural Integrity Procedia 00 (2019) 000 – 000

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Table 1: Geometry data for the model. Description

Variable name

Length (mm)

H T

Height of the tab

1 2

H LAM

Height of the laminate

H A

Height of the adhesive layer

0,04

W

Width of the specimen

10 80 20

L G L T

Length of the gauge section

Length of the tab

All models were loaded with a nominal load of F = 1000 N. The Force was applied to a reference node, which is connected with rigid elements to the upper contact surface between tab and clamping. Since the clamping is symmetric, the displacement in the negative Z-direction of the upper surface, which is a result of the clamping force F C , is coupled by equations to the lower contact surface in positive Z-direction. Furthermore, no tilting of the contact surfaces and no displacement in the Y-direction was allowed.

Fig. 2: Schematic representation of the clamping. All materials were considered as linear elastic, where aluminum and the adhesive were isotropic, CFRP transversally isotropic, and GFRP was modeled as an orthotropic material computed from UD data with a ±45° layup (i.e. 1-direction = X - axis). The material data used in the simulations are listed in Table 2.

Table 2: Material data used in the model. Name E 1 (GPa)

ν 12 (-)

ν 23 (-)

E 2 (GPa)

E 3 (GPa)

G 12 (GPa) G 23 (GPa)

CFRP plies

135.0

7.3

7.3

0.3

0.4

4.4

2.28

GFRP woven fabric tabs 16.4

16.4

10.3

0.549

0.277

9.785

2.7

Aluminum tabs

80

0.34 0.34

Adhesive

5

In order to compute the influence of the material of the tabs and the taper angle α, the models listed in Table 3 were considered. For the evaluation, the first two CFRP plies and the adhesive were assessed. The failure criterion of Puck (Puck 1996) was used for the CFRP plies and for the adhesive, the Mises stress was used for the qualitative comparison. For this purpose a user subroutine (UVARM) was used in Abaqus which computes the Puck 3D risk parameter defined as the ratio of acting stress divided by the allowable stress (Schuecker et al. 2006). The strength values and puck parameters are given Table 4. The model names introduced here are composed of the abbreviation of the material plus the taper angle.