PSI - Issue 39

Mario Álvarez-Blanco et al. / Procedia Structural Integrity 39 (2022) 379–386 Author name / Structural Integrity Procedia 00 (2021) 000–000

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Fig. 8. Three-point bending tests results for no-shell specimens with XY plane orientation.

It is simple to observe that, as the infill core density of the samples increases, the maximum force during bending increases too. In the case of the 30% specimen, its fracture is progressive, reaching large displacements but not the complete fracture. The jumps represented in this curve were verified by the DIC results as gradual breaks in each joint of the inner pattern along the crack path. By contrast, this high plasticity does not appear for the 50% and 75% specimens. Instead, the complete fracture is abrupt and occurs after a small displacement. For the corresponding rotated samples with XZ plane orientation, the experimental results are similar, keeping the same relation between infill core density and maximum force. 3.3. Crack morphology in tested samples The influence of the grid pattern on the fracture nucleation and growth in XZ orientated specimens with one shell will be examined under three-point bending tests. Fig. 9 shows the one-shell specimens results (down) with their corresponding inner pattern (up). The images are taken from the tensile side of the samples. The bending test generates a crack , growing normal to the tensile stresses at the bottom face. Note that the nucleation of the fracture in the shell of each specimen is localized at empty voids of the grid, and then its growth is also influenced by the lattice core.

Fig. 9. Correlation between grid pattern and crack path.