Universal testing machine

Abstract: Additive manufacturing (AM), more commonly referred to as 3D printing, has become increasingly popular for rapid prototyping (RP) purposes by hobbyists and academics alike. In recent years AM has transitioned from a purely RP technology to one for final product manufacturing. As the transition from RP to manufacturing becomes an increasingly accepted practice it is imperative to fully understand the properties and characteristics of the materials used in 3D printers. This paper presents the methodology and results of the mechanical characterization of acrylonitrile butadiene styrene (ABS) and polycarbonate (PC) 3D printed parts to determine the extent of anisotropy present in 3D printed materials. Specimens were printed with varying raster ([+45/−45], [+30/−60], [+15/−75], and [0/90]) and build orientations (flat, on-edge, and up-right) to determine the directional properties of the materials. Reduced gage section tensile and Isopescu shear specimens were printed and loaded in a universal testing machine utilizing 2D digital image correlation (DIC) to measure strain. Results indicated that raster and build orientation had a negligible effect on the Young’s modulus or Poisson’s ratio in ABS tensile specimens. Shear modulus and shear yield strength varied by up to 33 % in ABS specimens signifying that tensile properties are not indicative of shear properties. Raster orientation in the flat build samples reveal anisotropic behavior in PC specimens as the moduli and strengths varied by up to 20 %. Similar variations were also observed in shear for PC. Changing the build orientation of PC specimens appeared to reveal a similar magnitude of variation in material properties.

Abstract: In the present work the morphology of natural fibers was correlated with their mechanical properties via image analysis. Jute, sisal, curaua, coir and piassava fibers were tested under direct tension in a universal testing machine and the cross-sectional areas of the fibers were calculated using images obtained in a scanning electron microscopy. For the jute fiber the tests were performed for several gage lengths in order to investigate its influence on the tensile strength and to compute the machine compliance. For sisal, jute and curaua fibers the amount of fiber-cells, the size of the cell walls and the real area of the fibers were measured and their correlation with the tensile strength addressed. The curaua fiber presented the highest mechanical performance with tensile strength and Young’s modulus of 543 MPa and 63.7 GPa, respectively. Weibull statistical analysis was used to quantify the variability of fiber strength. The sisal fibers presented the highest Weibull modulus (3.70), whereas the curaua presented the lowest one (m = 2.2), which means that the sisal had the lowest variability and curaua the highest.

Abstract: Statement of problem The application of 3-dimensional printing technology is emerging in dentistry and is being increasingly used to fabricate dental restorations. To date, scientific evidence is lacking regarding the effect of different factors on the mechanical properties of the printed restorations with the additive manufacturing technique. Purpose The purpose of this in vitro study was to evaluate the effect of build direction (layer orientation) on the mechanical properties of a novel 3-dimensionally (3D)-printed dental restorative material. Material and methods Based on the printing direction, 2 groups were tested. In the first group (n=20), the specimens were vertically printed with the layers oriented perpendicular to the load direction. In the second group (n=20), the specimens were horizontally printed with the layers oriented parallel to the load direction. All specimens were fabricated using the DW028D 3D-printer. The specimens were loaded with a universal testing machine at a crosshead speed of 1 mm/min with a 10-kN load cell. The test was performed at room temperature (22°C) under dry testing conditions. The compressive strength was calculated for both groups, and the results were compared using the unpaired t test (α=.05). Results The mean ±SD compressive strength for the vertically printed specimens was 297 MPa (±34) compared with 257 MPa (±41) for the horizontally printed specimens ( P =.002). Conclusions Within the limitations of this study, the layer orientation was found to influence the compressive strength of the material. Vertically printed specimens with the layers oriented perpendicular to load direction have improved mechanical properties more than horizontally printed specimens with the layers oriented parallel to load direction.