PSI - Issue 33

Mauro Ricotta et al. / Procedia Structural Integrity 33 (2021) 695–703 Author name / Structural Integrity Procedia 00 (2019) 000–000

699

5

Therefore, it can be concluded that a brittle and quasi-brittle macroscopic behaviour characterises the quasi-static tensile tests on notched specimens, as also noted by Vielle et al (2011) and Vielle et al (2016).

200

(b)

12 16 20

(a)

17.5

15.9

13.1

12.1

150

10.1

8.9

8.0

0 4 8

100

5.2

4.2

3.4

 [MPa]

1.1

0.4

Fibre content [%]

0° 45° 90°

50

0

[0;0.04)

0

0.005

0.01

0.015

0.02

[0.16;0.2) Fiber length [mm] [0.2;0.24)

[0.36;0.4)

[0.4;0.44)

[0.04;0.08)

[0.08;0.12)

[0.12;0.16)

[0.24;0.28)

[0.28;0.32)

[0.32;0.36)

[0.44;0.48]

 [mm/mm]

Fig. 3. (a) Fibre length distribution and (b) engineering stress-engineering strain curves of unnotched GF40-PPS specimens.

(b)

0 0.5 1 1.5 2 2.5 3 3.5

(a)

0 0.5 1 1.5 2 2.5 3 3.5

90_R025_1 90_R05_1 90_R1_1 90_R2_1 90_R5_1 90_R10_1 R=0. mm R=0. mm R=1 mm R=2 mm R=5 mm R=10 mm

0_R025_1 0_R05_1 R=0. 5 mm R=0. mm

0_R1_1 0_R2_1 0_R5_1 R=1 mm R=2 mm R=5 mm

Tensile load [kN]

Tensile load [kN]

Fibre orientation,  =90°

Fibre orientation,  =0°

0

0.2

0.4

0.6

0.8

0

0.2

0.4

0.6

0.8

Displacement [mm]

Displacement [mm]

Fig. 4. Tensile load-displacement curves for notched (a)  =0° and (b)  =90° specimens. The theoretical stress concentration factors referred to the net section, K tn , relevant to the notched geometries were calculated through 3D linear elastic finite element analyses carried out with the commercial software ANSYS ® , by using 8-node SOLID185 elements along with the elastic material properties listed in Table 3. To account for the machine grip effect in the numerical models, displacements were applied to the lines highlighted in Fig. 2. The results of the quasi static tests carried out on notched geometries were reanalysed in terms of ultimate tensile net-stress strength,  n,UTS , calculated by simply dividing the ultimate applied load by the net-area of the specimen, and they are plotted against K tn in Fig. 5a and 5b for  =0° and  =90°, respectively. In the same figures, the following two limiting conditions are also reported: i. on the left-hand side, the asymptote corresponding to a full notch sensitivity condition, according to which the static strength of notched geometries is estimated dividing the material strength by the theoretical stress concentration factor,  UTS /K tn ; ii. on the right-hand side, the asymptote corresponding to the strength of the sharp V (zero root radius) notch, V UTS  , which was estimated as the strength of the V notch case with R=0.25 mm. This last-mentioned choice is fully justified by the fact that the region in front of the notch tip, where the stress distribution of the rounded notch with R=0.25 mm significantly differs from that of the corresponding sharp V (zero root radius) notch has a very limited