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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4.3. Classical Laminate Theory

To compare the stresses applied to the embedded 90°-plies with the stresses applied to the UD 90°-plies some calculations were necessary. The well-known Classical Laminate Theory (CLT) (Altenbach et al. 2018; Jones 1999; Schürmann 2005) was used to transform the stresses applied to the EMB090 from the whole specimen (including the 0°-plies) to the embedded 90°-plies. The Young´s modulus in fibre direction E 1 , the shear modulus G 12 and the shear strength S were taken from data sheet. The Young´s modulus transvers to fibre direction E 2 and the tension strengths transverse to fibre direction Y T from quasi-static tests in section 5.1 – Quasi-static results and the Poisson´s ration ν 12 from results of previous work with a similar material (Brunbauer and Pinter 2015).

5. Results of experimental tests

In the following, the results of quasi-static and fatigue tests are presented and discussed. In accordance with section 4 the discussion of the results will start with quasi-static test results. Afterwards the results of fatigue tests will be discussed.

5.1. Quasi-static results

The experimentally measured geometry data as well as the quasi-static properties for specimens are listed in Table 6. Fig. 6 shows the engineering stress σ versus the engineering strain ε for UD90 (left) and EMB090 (right). As expected, the specimen strength for the EMB090 is much higher than for the UD90. All of the curves for the EMB090 show a low scattering of the different specimens up to an engineering stress of around 435 MPa. Above this stress level the embedded 90° layers start to crack and the curves show a big scattering. For UD90 the curves show an almost identical course which is an indication for a uniform production of the specimen.

Fig. 6: Engineering stress versus engineering strain (measured with DIC) for UD90 (left) and EMB090 (right).

Table 6: Measured geometry details and quasi-static properties of EMB090 and UD90. Specimen Width Thickness

Young’s modulus Eng. Stress

Poisson's ratio

[mm] 25.03

[mm]

[GPa]

[MPa]

[-]

EMB090

Mean

1.79 0.02 2.30 0.03

41

550

0.03 0.00

Std. Dev.

0.03

1.7

50

UD90

Mean

25.03

8.08 0.06

70

0.017 0.008

Std. Dev.

0.17

5.9