PSI - Issue 8
V. Dattoma et al. / Procedia Structural Integrity 8 (2018) 444–451 Author name / Structural Integrity Procedia 00 (2017) 000–000
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Table 4. Experimental results of OHC mechanical tests. Specimen Set F OHC [MPa]
ε max [%]
mean 0.588 0.676 0.705 0.680 0.570
st. dev.
mean 2.632 2.557 1.464 2.274 1.513
st. dev.
0.038 0.042 0.028 0.028 0.030
- - - - -
50-33-24-WD10 50-33-24-WD20 50-33-24-WD40 17-67-24-WD10 25-50-16-WD10
Observing the data, in particular comparing the data of the first three series that differs only for the geometry of the wrinkles, it is possible to notice that the presence of wrinkles is generally more important in the case of an increased curvature, confirming that the ratio W/D = 10 represents the most critical situation. This is particularly true in the case of compression tests, while the difference is not substantial in traction. From a qualitative point of view the presence of wrinkle determines in traction an anomalous behaviour at the half of the load corresponding to failure that corresponds to a local damage in correspondence of the critical section (Fig. 5). With ratio W/D larger than 10, the global behaviour of the specimen is not influenced by the presence of the artificial wrinkle. In compression, the presence of wrinkles determines a change of the slope of the stress-strain curves (Fig. 6) that could explain the values of strain to failure widely different from the behaviour of pristine material. The different lay-up does not alter the general behaviour described before, since the knockdown factor seem not influenced particularly by lower stiffness and strength of the laminates having a lower percentage of 0° plies.
Fig. 5. Comparison of typical stress-strain curves: OHT tests.
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