PSI - Issue 41

Daniele Gaetano et al. / Procedia Structural Integrity 41 (2022) 439–451 Author name / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 7. Comparison between Direct Numerical Simulation (DNS) and Multiscale Numerical Simulation (MNS): (a) Diffuse Interface Model with a mapped mesh; (b) Diffuse Interface Model with a random mesh; (c) Single Interface Model.

3.2. Mixed-mode fracture test on a L-shaped composite panel The second case study considered here is a mixed-mode fracture test performed on a L-shaped composite panel, widely studied in the literature for both homogeneous (see, for instance, Meschke and Dumstorff (2007) and therein references) and heterogeneous (Oliver et al. (2017)) materials. The geometry and boundary conditions of this test are reported in Fig. 8, together with the unstructured mesh adopted for the Multiscale Numerical Simulations (MNSs). The same microstructure considered in the previous case study is assumed, and the same elastic and inelastic parameters reported in Tables 1 and 2 are used. Fig. 9 shows the results of the Multiscale Numerical Simulation in terms of deformed configuration and first principal stress map at the final simulation step (Fig. 9a) as well as of force-displacement curve (Fig. 9b). Fig. 9b also shows a comparison with a Direct Numerical Simulation (DNS), performed on a fully meshed specimen. In particular, an overestimation of the peak strength and an underestimation of the post-peak strength are experienced. These discrepancies are probably due to a combined effect of the two following sources of error: (i) the mixed-mode fracture is totally neglected in the proposed nonlinear homogenization scheme; and (ii) the boundary layer effects, although being important in the considered geometry configuration, are not captured in the proposed multiscale approach. However, the resulting overall error on the peak load is fully acceptable from an engineering point of view, being of about 4%. These results confirm the reliability of the proposed multiscale modeling approach also in the case of mixed-mode fracture conditions, at least in terms of global structural response.

Fig. 8. L-shaped composite panel subjected to a mixed-mode fracture test: (a) geometry and boundary conditions (all dimensions are expressed in μm); (b) unstructured mesh used for Multiscale Numerical Simulation.