PSI - Issue 50

Kirill Guseinov et al. / Procedia Structural Integrity 50 (2023) 105–112 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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(a) (b) Fig. 4. Shear stress-strain curves under biaxial loading of cubic (a) and V-notched (b) specimens

3.3. Analysis of strength properties

The obtained experimental data of interlaminar shear strength under through-thickness compression of cubic and V-notched specimens was compared with Daniel theory. Daniel failure curve parameters were identified from preliminary static tests. The interlaminar shear modulus of G 13 =3.6 GPa was determined using the improved three point bending test method described in Guseinov et al. (2022). The through-thickness modulus of E 3 =12 GPa was de termined from compression tests of cubic specimens with zero cut angle α. The interlaminar shear strength of F 13 =48.4 MPa was determined from testing specimens using short beam method in accordance with ASTM D790-07 (2010). The average interlaminar shear and through-thickness compressive stresses at different loading angles are given in Table 1.

Table 1. Experimental assessment of stresses using two methods under biaxial loading

Interlaminar shear stresses (MPa)

Through-thickness compression stresses (MPa)

Difference in Interlaminar Shear Stresses

Difference in Through Thickness Stresses

Loading angle

Cubic specimens 83.8 ± 6.2 86.1 ± 2.2 78.9 ± 4.0 74.6 ± 4.8

V-notched specimens

Cubic specimens

V-notched specimens

15 20 25 30 35 40 45

-

312.6 ± 22.9 236.6 ± 5.9 172.8 ± 5.1 129.2 ± 8.3

-

-

-

90.3 ± 0.7 84.1 ± 1.6 76.9 ± 1.2 74.7 ± 0.8 67.3 ± 1.1 61.7 ± 0.9

248.2 ± 2.0 180.3 ± 3.4 129.5 ± 2 .0 104.5 ± 0.5 79.2 ± 1.9 61.7 ± 0.9

4.6 6.2 3.0

4.7 4.2 0.2

- -

- -

- -

- -

55.4 ± 1.0

55.4 ± 1.0

10.2

10.2

Figure 9 shows the comparison of the interlaminar shear strength, assessed on cubic and V-shaped specimens with NU-Daniel theory. In both cases, there is good agreement with the failure curve. At the same time, the experimental values of the interlaminar shear strength were more repeatable on the new fixture. The buckling of