<p>The design of these lattice structures in the material at micro and millimeter scales has become prevalent in the literature worldwide to attain lightweight and strong engineering applications. Due to the complex network of strut members designed at small scales, the fabrication of these lattice structures is only possible by using the recently developed additive manufacturing technologies. On the other hand, because of the layer by layer manufacturing process, there exist micro- and milli meter scale variations and uncertainties on the geometry and material of the strut members in the designed lattice structures when fabricated. There have been many studies in the literature regarding the characterization of uncertainties, but the changes dependent on the location of the strut elements are usually ignored. Therefore, when the lattice structures designed on the computer are fabricated by additive manufacturing processes, there becomes a discrepancy between the performance of the designed structure and the additively manufactured structure. The content of this study is to evaluate the differences between the tensile test results of individual strut members fabricated by the material extrusion process and finite element analysis predictions of the struts modeled with the geometric variations introduced by the material extrusion method using advanced statistical methods based on the spatial dependency. For this purpose, strut member specimens with different diameter values and angles are fabricated using the material extrusion technique from PLA material. The fabricated strut specimens are examined by a digital light microscope and the measurements are done for the fabricated diameter variations. These variations are characterized using the random field method which is commonly used for modeling the spatially dependent variations. These variations modeled by the random field method are integrated into the finite element models by using voxel elements. The mechanical properties of the PLA are characterized by the tensile test of the filament used for material extrusion. Tensile tests of the fabricated strut specimens at different diameters and build angles are also conducted. The results of the finite element analysis that includes the fabricated specimen models with spatial variations are compared with the tensile test results obtained for the fabricated strut specimens. The finite element models are also constructed with the random variable approach without the spatial dependency consideration for comparison. The reasons of differences from the experimental results are discussed and solutions to improve the prediction accuracy are presented. The developed model can be extended to different additive manufacturing techniques and the variations observed in the fabricated geometry and material properties can be characterized.</p>

Evaluation of Differences Between FEA Predictions With Geometric Variations and Tensile Tests of Strut Specimens of Lattice Structures Fabricated by Material Extrusion

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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