It is discovered in this investigation that there exist two different failure modes and a special separation angle which is the demarcation point of the two different failure modes when FDM (Fused Deposition Modelling) 3D printing materials fail under a tensile load. In order to further understand the mechanical properties of FDM 3D printing materials and promote the use of FDM 3D printing materials, their tensile failure strengths at different printing angles and separation angles are measured and analysed theoretically. A new separate-modes of transversely isotropic theoretical failure model is established to predict the tensile failure strength and separation angle of FDM 3D printing PLA (polylactic acid) material based on the hypothesis of transverse isotropy and the classical separate-modes failure criterion. During this research, the tensile specimens designed according to the current test standard ISO (527-2-2012) for plastic-multi-purpose specimens are fabricated in 7 different printing angles ( 0 ∘ , 15 ∘ , 30 ∘ , 45 ∘ , 60 ∘ , 75 ∘ , 90 ∘ ) and three levels of printing layer thickness (0.1 mm, 0.2 mm, 0.3 mm). Experimental results show that the tensile failure strength increases with the increase of the printing angle or the decrease of the layer thickness. Meanwhile, inter-layer failure tends to occur when the printing angle is small and in-layer failure tends to occur when the printing angle is big. In comparison with the results predicted by the established theoretical model, all values of the Generalized-Relative-Root-Mean-Square Error are close to zero and the experimental separation angles are also between 45 ∘ and 60 ∘ . So the predictive capacity of the theoretical model is affirmed by experimental results.

Tensile failure strength and separation angle of FDM 3D printing PLA material: Experimental and theoretical analyses

Fatigue behaviour of FDM-3D printed polymers, polymeric composites and architected cellular materials

Nowadays, one of the most studied technologies for obtaining different parts is Additive Manufacturing (AM) Whether it is about plastic or metal materials, AM is used because very complex parts can be obtained, without further technological operations From all AM technologies, Fused Deposition Modeling (FDM) is the most used all over the world, due to its cost-effective way of printing FDM is based on the extrusion of a wire, through which a piece is formed by successively depositing layer-by-layer of molten material This paper experimentally investigates the tensile properties of 3D printed specimens obtained through FDM printing The influence of spatial printing direction (0°, 45°, 90°) and size effect (different thickness) on main mechanical properties was investigated Polylactic acid (PLA) dog bone specimens were adopted for all tensile tests Experimental tests were carried out at room temperature, according to ISO 527-1 Standard It was observed that the spatial orientation has less influence on the Young modulus and higher influence on the tensile strength Furthermore, increasing the number of layers leads to decreasing of both the Young modulus and tensile strength

Effect of manufacturing parameters on tensile properties of FDM printed specimens

In nature, mesoscopic or microscopic cellular structures like trabecular bone, wood, shell, and sea urchin, can have high load-carrying capacity. These cellular structures with diverse shapes, forms and designs can be mainly classified into open and closed cell cellular structures. It is difficult to replicate these natural complex lattice structures with traditional manufacturing, but additive manufacturing (AM) technology development has allowed engineers and scientists to mimic these natural structures. Fabricating close cell lattice structures is still considered difficult due to the support structure within the lattices. This paper evaluates a novel way of fabricating a close cell lattice structure with a material extrusion process. The design eliminates the need for support structures and the subsequent post-processing required to remove them. A shell-shaped close cell lattice structure bio-mimicking a sea urchin shape was introduced for the load-bearing structure application. The mechanical properties of the proposed structure, including stiffness, deformation behavior and energy absorption, were compared with those of benchmarked honeycomb and open cell sea urchin (SU) lattice structures of the same density. SU lattice structures and honeycomb periodic lattice structures with varied sizes but the same morphology and fixed density were designed and printed in polylactic acid material (PLA). Their physical characteristics, deformation behavior, and compressive properties were investigated experimentally and via finite element analysis. The effect of the unit cell size on mechanical properties was studied and discussed, and the rankings of better performances were drawn. A possible application of the closed cell is for fabricating the load bearing structure; it can also be encapsulated within a fluid to impart strength and damping characteristics.

Yuansong Chen

Papers

Novel mechanical models of tensile strength and elastic property of FDM AM PLA materials: Experimental and theoretical analyses