scholarly journals Creep Behavior of Polyamide 12, Produced By Selective Laser Sintering With Different Build Orientations

2021 ◽  
Author(s):  
Maximilian Krönert ◽  
Thomas Josef Schuster ◽  
Felix Zimmer ◽  
Jens Holtmannspötter
Keyword(s):  
Creep Behavior ◽  
Significant Influence ◽  
Selective Laser Sintering ◽  
Tensile Tests ◽  
Laser Sintering ◽  
Creep Tests ◽  
Build Orientation ◽  
Polyamide 12 ◽  
Static Tensile ◽  
Term Creep

Abstract The successful use of components, produced by selective laser sintering as a rapid manufacturing process, requires a comprehensive understanding of the material. In this study, the effect of specimen build orientation on the mechanical properties of selective laser sintered polyamide 12 was investigated in detail. Samples were printed with an orientation of 0°, 15°, 45° and 90° to the build platform. Additionally to quasi-static tensile tests, Creep tests under different loads (5 MPa, 10 MPa, 15 MPa and 20 MPa) and for different times (10 hours and 1,000 hours) with and without relaxation were performed. Creep behavior was analyzed using the Burgers model. Therefore, the elastic strain, the relaxant strain, the viscous strain and the total deformation were determined. Results show that the build orientation has no significant influence on the long-term creep behavior, at small stresses. Short-term creep and relaxation tests show, that the elastic and viscous strain are only slightly influenced by the build orientation. However, the viscoelastic strain is affected by the build orientation. Furthermore, the deformations resulting from creep and relaxation have no significant influence on the mechanical behavior as shown by tensile tests.

Orthotropic properties of cement-filled polyamide 12 manufactured by selective laser sintering

2020 ◽  
Vol 26 (6) ◽  
pp. 1103-1112
Author(s):  
Saleh Ahmed Aldahash ◽  
Abdelrasoul M. Gadelmoula
Keyword(s):  
Mechanical Properties ◽  
Laser Energy ◽  
Flexural Modulus ◽  
Selective Laser Sintering ◽  
Scanning Speed ◽  
Laser Sintering ◽  
Content Type ◽  
Build Orientation ◽  
Polyamide 12 ◽  
Fabrication Parameters

Purpose The cement-filled PA12 manufactured by selective laser sintering (SLS) offers desirable mechanical properties; however, these properties are dependent on several fabrication parameters. As a result, SLS prototypes may exhibit orthotropic mechanical properties unless properly oriented in build chamber. This paper aims to evaluate the effects of part build orientation, laser energy and cement content on mechanical properties of cement-filled PA12. Design/methodology/approach The test specimens were fabricated by SLS using the “DTM Sinterstation 2000” system at which the specimens were aligned along six different orientations. The scanning speed was 914mm/s, scan spacing was 0.15mm, layer thickness was 0.1mm and laser power was 4.5–8Watt. A total of 270 tensile specimens, 270 flexural specimens and 135 compression specimens were manufactured and the tensile, compression and flexural properties of fabricated specimens were evaluated. Findings The experiments revealed orientation-dependent (orthotropic) mechanical properties of SLS cement-filled PA12 and confirmed that the parts with shorter scan vectors have enhanced flexural strength as compared with longer scan vectors. The maximum deviations of ultimate tensile strength, compressive strength and flexural modulus along the six orientations were 32%, 26% and 36%, respectively. Originality/value Although part build orientation is a key fabrication parameter, very little was found in open literature with contradictory findings about its effect on mechanical properties of fabricated parts. In this work, the effects of build orientation when combined with other fabrication parameters on the properties of SLS parts were evaluated along six different orientations.

scholarly journals Investigation of porosity behavior in SLS polyamide-12 samples using ex-situ X-ray computed tomography

2021 ◽  
Vol 39 (3) ◽  
pp. 436-445
Author(s):  
Grzegorz Ziółkowski ◽  
Emilia Grochowska ◽  
Dawid Kęszycki ◽  
Piotr Gruber ◽  
Viktoria Hoppe ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Tensile Test ◽  
Selective Laser Sintering ◽  
Tensile Tests ◽  
Ex Situ ◽  
X Ray ◽  
Polyamide 12 ◽  
Before And After ◽  
Static Tensile ◽  
X Ray Computed

Abstract The paper presents a detailed description of the method of carrying out static tensile tests in ex-situ X-ray computed tomography (XCT) conditions. The study compares samples manufactured with the use of additive technology in two orientations, horizontally and vertically, which correspond to the in-layer and between-layer sintering mechanisms. Both the fracture mechanism and porosity behavior differed significantly for the two manufacturing directions. The conducted analysis made it possible to compare the changes in porosity, the number of pores, and also their diameters and shape before and after the tensile test. This allows for in-depth identification and better understanding of the phenomena occurring during the static tensile test of polyamide-12 samples manufactured using selective laser sintering (SLS) technology.

Study in performance and morphology of polyamide 12 produced by selective laser sintering technology

2018 ◽  
Vol 24 (5) ◽  
pp. 813-820 ◽  
Author(s):  
Junjie Wu ◽  
Xiang Xu ◽  
Zhihao Zhao ◽  
Minjie Wang ◽  
Jie Zhang
Keyword(s):  
Selective Laser Sintering ◽  
Polarized Light ◽  
Chain Scission ◽  
High Energy ◽  
Laser Sintering ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Content Type ◽  
X Ray ◽  
Polyamide 12

Purpose The purpose of this paper is to investigate the effect of selective laser sintering (SLS) method on morphology and performance of polyamide 12. Design/methodology/approach Crystallization behavior is critical to the properties of semi-crystalline polymers. The crystallization condition of SLS process is much different from others. The morphology of polyamide 12 produced by SLS technology was investigated using scanning electron microscopy, polarized light microscopy, differential scanning calorimetry, X-ray diffraction and wide-angle X-ray diffraction. Findings Too low fill laser power brought about bad fusion of powders, while too high energy input resulted in bad performance due to chain scission of macromolecules. There were three types of crystal in the raw powder material, denoted as overgrowth crystal, ring-banded spherulite and normal spherulite. Originality/value In this work, SLS samples with different sintering parameters, as well as compression molding sample for the purpose of comparison, were made to study the morphology and crystal structure of sintered PA12 in detail.

Rate Dependence and Short-Term Creep Behavior of a Thermoset Polymer at Elevated Temperature

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
C. M. Falcone ◽  
M. B. Ruggles-Wrenn
Keyword(s):  
Creep Behavior ◽  
Viscoelastic Model ◽  
Rate Sensitivity ◽  
Monotonic Loading ◽  
Stress Rate ◽  
Creep Tests ◽  
Strain Behavior ◽  
Thermoset Polymer ◽  
Term Creep ◽  
Prior Stress

The inelastic deformation behavior of PMR-15 neat resin, a high-temperature thermoset polymer, was investigated at 288°C. The effect of loading rate on monotonic stress-strain behavior as well as the effect of prior stress rate on creep behavior were explored. Positive nonlinear rate sensitivity was observed in monotonic loading. Creep response was found to be significantly influenced by prior stress rate. The effect of loading history on creep was studied in stepwise creep tests, where specimens were subjected to a constant stress rate loading followed by unloading to zero stress with intermittent creep periods on both loading and unloading paths. The strain-time response was strongly influenced by prior deformation history. Negative creep was observed on the unloading path. In addition, the behavior of the material was characterized in terms of a nonlinear viscoelastic model by means of creep and recovery tests at 288°C. The model was employed to predict the response of the material under monotonic loading/unloading and multistep load histories.

scholarly journals Selective laser sintering of copper filled polyamide 12: Characterization of powder properties and process behavior

2018 ◽  
Vol 40 (5) ◽  
pp. 1801-1809 ◽  
Author(s):  
Lydia Lanzl ◽  
Katrin Wudy ◽  
Sandra Greiner ◽  
Dietmar Drummer
Keyword(s):  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Polyamide 12 ◽  
Process Behavior ◽  
Powder Properties

scholarly journals Hybrid Approaches for Selective Laser Sintering by Building on Dissimilar Materials

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5285
Author(s):  
Babette Goetzendorfer ◽  
Thomas Mohr ◽  
Ralf Hellmann
Keyword(s):  
Substrate Surface ◽  
Selective Laser Sintering ◽  
Dissimilar Materials ◽  
Polyamide 6 ◽  
Laser Sintering ◽  
New Approach ◽  
Metallic Substrates ◽  
Polyamide 12 ◽  
Melting Temperatures ◽  
Hybrid Approaches

We introduced a new approach in selective laser sintering for hybrid multicomponent systems by fabricating the sintered polyamide 12 (PA12) part directly onto a similar (PA12) or dissimilar (polyamide 6 (PA6) and tool steel 1.2709) joining partner. Thus, the need for adhesive substances or joining pressure was completely circumvented, leading to the possibility of pure hybrid lightweight bi-polymer or metal–polymer systems. By taking advantage of the heating capabilities of the sinter laser regarding the substrate surface, different exposure strategies circumvented the lack of overlapping melting temperatures of dissimilar polymers. Therefore, even sintering on non-PA12 polymers was made possible. Finally, the transfer on metallic substrates—made up by selective laser melting (SLM)—was successfully performed, closing the gap between two powder-based additive processes, selective laser sintering (SLS) and SLM.

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