13th International Conference on Fracture June 16–21, 2013, Beijing, China -9- Figure 3. The finite elements mesh at the crack tip. Figure 4. Numerical and experimental results for mixed mode loading The fractured sandwich beam is modeled according to a mesh generator proposed in [5] which imposes the discretion of the areas of the beam regarding the mesh density and quality in three different regions according to the length of the crack and to crack distance from the upper interface [5]. This discretion is a prerequisite in order to avoid the worthless consumption of computational resources and time. The model shown in Fig. 3 corresponds to the maximum crack length a 70mm ≈ in which about 22500 elements have been used in the finite element analysis. The experimental data and the numerical predictions according to the proposed cohesive law are shown in Figure 4. At the load at failure (P 1422N ) kinking of the crack into the core and catastrophic failure was observed. 5. Conclusions. In this paper two procedures have been considered for lightweight structures in order to simulate crack propagation and kinking into the core of sandwich structures very close to the upper skin
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