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

373

4

Table 3: List of model configurations evaluated. Modell

Taper angle α (°)

Tab material Aluminum Aluminum GFRP fabric GFRP fabric

ALU90 ALU14 GFRP90 GFRP14

90 14 90 14

Table 4: Strength and puck parameters for the CFRP plies. Name X T (MPa) X C (MPa) Y T (MPa)

Y C (MPa) S (MPa)

p 12

p

p

p

+ (-)

- (-)

+ (-)

- (-)

12

23

23

CFRP

1748

1535

116

200

90

0.27

0.27

0.35

0.3

The results of the simulations were evaluated at paths in the first ply, the second ply and in the adhesive layer. They are shown schematically in Fig. 1. In the CFRP plies, the paths are located near the bottom of the ply at one percent of the height of the ply. The path in the adhesive is located at half of the height of the adhesive layer. For each of these locations, two paths were evaluated at the edge and the center in width direction of the specimen ( Y = 0.1 mm and Y = 5 mm). The paths in the plies cover the area along the length of the specimen from the gauge section to the tabs and start at X = -5 mm and end at X = 10 mm. In the adhesive layer, they start at the beginning of the tabs at X = 0 mm and end at X = 10 mm. For comparison of the stress concentrations near the end of the tabs the risk parameter computed by Puck 3D is normalized by the average of the risk parameter in the gauge section for each respective ply, where the stress concentration caused by the clamping was subsided ( X = -6 mm to X = -2 mm). The normalized Puck 3D risk parameters for the first (0°) and the second (90°) ply along the path are shown in Fig. 3. The comparison between the models generally shows, that GFRP fabric with a taper angle of 14° achieves the best results and the distribution of the Mises stress in the adhesive layer (shown in Fig. 4) does not have high stress concentrations at the end of the tab for this configuration. This leads to a more uniform transfer of stresses into the laminate. For all configurations, the risk parameter peaks at the end of the tab in the 0° plies (see Fig. 3 (a)). The different versions of the tabs have a significant influence on this peak of the risk parameter. Tabs without taper angle (ALU90 and GFRP90) lead to a higher risk of failure than tabs with the small taper angle (ALU14 and GFRP14). The comparison of the different materials shows, that the GFRP fabric also reduces the risk substantially for the 0° ply. The comparison between the best (GFRP14) and the worst (ALU90) performing tab shows a reduction of the risk parameter form 4.5 to 1.3 in the center of the specimen. The difference between the center of the specimen and the edge is relatively small compared to the other differences.

Fig. 3: Normalized Puck 3D risk parameter in the 0° ply (left) and the 90° ply (right) over X-distance from the end of the tab, for all models.