Issue 49

H. Araújo et alii, Frattura ed Integrità Strutturale, 49 (2019) 478-486; DOI: 10.3221/IGF-ESIS.49.45 483 Finite element results are shown as the von Mises stress distribution (Fig. 5), as well as load-displacement curves at the end of simulation tests (Fig. 6). As can be seen from Fig. 5, the stress distribution is not uniform along the cellular arrangement, and one may infer that there will be localized deformation and subsequent failure at specific zones of the arrangement. The three arrangements loaded at 0º show the possibility of deformation damage at mid sections, while in the other two cases (45º and 90º), oblique bands are to be found. These findings are in accordance with experimental failure observations (Fig. 3), with the exceptions of Honeycomb_45 and Lotus_45. The failure modes differ with the loading direction either in experimental or simulation testing. Honeycomb Lotus Plateau 0 45 90 Figure 5: Finite element analysis of stress after compression of geometries Honeycomb, Lotus and Plateau configurations for PLA at directions 0, 45 and 90 (von Mises stress (MPa)). The simulated force–displacement curves are shown in Fig. 6 for all the arrangements and the three loading directions. The shape of the curves was unchanged for all the geometries and loading directions with an initial linear part followed by a nonlinear region. For each angle the curves differ between configurations, namely in the initial slope and in maximum load attained (with the exception of Plateau_0 and Honeycomb_0). In the 0º and 45º conditions the same trend is verified, with the lotus configuration exhibiting the highest load, followed by the honeycomb geometry and finally by the Plateau arrangement. For 90º case, lotus still shows the highest load. A comparison of Fig. 4 with Fig. 6 shows that experimental and simulation curves exhibit similar shapes. However, there are differences in the load values between simulation and experimental results. The differences may be due to the non- homogeneity of the experimental specimens obtained by FDM. In fact, although the infill parameter was taken to be 100 %, thinner struts may be formed only by the contour lines and possess no infill material which give rise to compact struts. Also the presence of small air gaps or other defects can be expected.