Abstract
Fused deposition modeling (FDM) uses lattice arrangements, known as infill, within the fabricated part. The mechanical properties of parts fabricated via FDM are dependent on these infill patterns, which make their study of great relevance. One of the advantages of FDM is the wide range of materials that can be employed using this technology. Among these, polylactic acid (PLA)-wood has been recently gaining attention as it has become commercially available. In this work, the stiffness of two different lattice structures fabricated from PLA-wood material using FDM are studied: hexagonal and star. Rectangular samples with four different infill densities made of PLA-wood material were fabricated via FDM. Samples were subjected to 3-point bending to characterize the effective stiffness and their sensitivity to shear deformation. Lattice beams proved to be more sensitive to shear deformations, as including the contribution of shear in the apparent stiffness of these arrangements leads to more accurate results. This was evaluated by comparing the effective Young’s modulus characterized from 3-point bending using equations with and without shear inclusion. A longer separation between supports yielded closer results between both models (~41% for the longest separation tested). The effective stiffness as a function of the infill density of both topologies showed similar trends. However, the maximum difference obtained at low densities was the hexagonal topology that was ~60% stiffer, while the lowest difference was obtained at higher densities (star topology being stiffer by ~20%). Results for stiffness of PLA-wood samples were scattered. This was attributed to the defects at the lattice element level inherent to the material employed in this study, confirmed via micro-characterization.
Highlights
In the optimization of weight without compromising mechanical properties, nature has made use of porous materials [1]
To avoid this property having a significant influence on the mechanical properties of the lattices, all the samples were fabricated with the same orientation with respect to the printing plane
The stiffness of Fused deposition modeling (FDM) samples with two different infill lattice patterns was characterized via 3-point bending
Summary
In the optimization of weight without compromising mechanical properties, nature has made use of porous materials [1]. This has inspired engineers and designers to explore the use of tessellated arrangements of matter, known as lattice materials [2,3]. Fused deposition modeling (FDM) or fused filament fabrication (FFF) makes use of a tessellated distribution of rasters known as infill. Each layer in the FDM process consists of contour rasters and infill patterns. While this leads to savings in materials and reduction in weight of the AM component, it affects their resulting mechanical properties [5]
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