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 Manufacturing of Porous Polycaprolactone Prepared with Different Particle Sizes and Infrared Laser Sintering Conditions: Microstructure and Mechanical Properties

2014 ◽  
Vol 6 ◽  
pp. 640496 ◽  
Author(s):  
G. V. Salmoria ◽  
D. Hotza ◽  
P. Klauss ◽  
L. A. Kanis ◽  
C. R. M. Roesler
Keyword(s):  
Mechanical Properties ◽  
Energy Density ◽  
Laser Energy ◽  
Flexural Modulus ◽  
Selective Laser Sintering ◽  
Polymeric Materials ◽  
Laser Sintering ◽  
Laser Energy Density ◽  
Particle Sizes ◽  
Mechanical Devices

The techniques of Rapid Prototyping, also known as Additive Manufacturing, have prompted research into methods of manufacturing polymeric materials with controlled porosity. This paper presents the characterization of the structure and mechanical properties of porous polycaprolactone (PCL) fabricated by Selective Laser Sintering (SLS) using two different particle sizes and laser processing conditions. The results of this study indicated that it is possible to control the microstructure, that is, pore size and degree of porosity, of the polycaprolactone matrix using the SLS technique, by varying the particle size and laser energy density, obtaining materials suitable for different applications, scaffolds and drug delivery and fluid mechanical devices. The specimens manufactured with smaller particles and higher laser energy density showed a higher degree of sintering, flexural modulus, and fatigue resistance when compared with the other specimens.

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.

Influence of energy density on polyamide 12 processed by SLS: from physical and mechanical properties to microstructural and crystallization evolution

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Tiago Czelusniak ◽  
Fred Lacerda Amorim
Keyword(s):  
Mechanical Properties ◽  
Surface Roughness ◽  
Energy Density ◽  
Laser Energy ◽  
Polymer Degradation ◽  
High Energy ◽  
Content Type ◽  
Polyamide 12 ◽  
Line Spacing ◽  
Scan Line

Purpose This paper aims to provide a detailed study on influence of the laser energy density on mechanical, surface and dimensional properties of polyamide 12 (PA12) parts produced by selective laser sintering (SLS), providing the microstructural and crystallization evolution of the samples produced at different energy densities. Design/methodology/approach Making use of a space filling design of experiments, a wide range of laser sintering parameters is covered. Surface morphology is assessed by means of profile measurements and scanning electron microscopy (SEM) images. Mechanical testing, SEM, X-ray diffraction (XRD), differential scanning calorimeter (DSC) and infrared spectroscopy (FTIR) were used to assess the influence of energy density on structural and mechanical properties. Findings Results show a high dependency of the properties on the laser energy density and also a compromise existing between laser exposure parameters and desired properties of laser sintered parts. Surface roughness could be associated to overlap degree when using higher scan line spacing values and lower laser speeds improved surface roughness when high scan line spacing is used. Higher mechanical properties were found at higher energy density levels, but excessively high energy density decreased mechanical properties. A transition from brittle to ductile fracture with increasing energy density could be clearly observed by mechanical analysis and SEM. XRD and DSC measurements show a decrease on the crystal fraction with increasing energy densities, which corroborated the plastic behavior observed, and FTIR measurements revealed polymer degradation through chain scission might occur at too high energy densities. Originality/value Valuable guidelines are given regarding energy density optimization for SLS of PA12 considering not only quality criteria but also microstructure characteristics. Surface properties are studied based on the concept of degree of overlap between laser scanning lines. For the first time, crystallization behavior of SLS PA12 parts produced at different energy levels was studied by means of XRD measurements. Polymer degradation of SLS PA12 parts was evaluated with FTIR, which is a non-destructive and easy test to be conducted.

scholarly journals Selective Laser Sintering of PA6: Effect of Powder Recoating on Fibre Orientation

2020 ◽  
Vol 4 (3) ◽  
pp. 108
Author(s):  
Tobias Heckner ◽  
Michael Seitz ◽  
Sven Robert Raisch ◽  
Gerrit Huelder ◽  
Peter Middendorf
Keyword(s):  
Computed Tomography ◽  
Mechanical Properties ◽  
Layer Thickness ◽  
Laser Power ◽  
Laser Energy ◽  
Fibre Orientation ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Shear Stresses ◽  
Imaging Results

In Selective Laser Sintering, fibres are strongly orientated during the powder recoating process. This effect leads to an additional increase of anisotropy in the final printed parts. This study investigates the influence of process parameter variation on the mechanical properties and the fibre orientation. A full factorial design of experiment was created to evaluate the processing parameters of recoating speed, layer thickness and laser power on the part’s modulus of elasticity. Based on the mechanical testing, computed tomography was applied to selected samples to investigate the process-induced fibre microstructure, and calculate the fibre orientation tensors. The results show increasing part stiffness in the deposition direction, with decreasing layer thickness and increasing laser power, while the recoating speed only shows little effect on the mechanical performance. This complies with computed tomography imaging results, which show an increase in fibre orientation with smaller layer thickness. With thinner layers, and hence smaller shear gaps, shear stresses induced by the roller during recoating increase significantly, leading to excessive fibre reorientation and alignment. The high level of fibre alignment implies an increase of strength and stiffness in the recoating direction. In addition, thinner layer thickness under constant laser energy density results in improved melting behaviour, and thus improved fibre consolidation, consequently further increasing the mechanical properties. Meanwhile, the parameters of recoating speed and laser power do not have a significant impact on fibre orientation within their applicable process windows.

A Round Robin study for Selective Laser Sintering of polyamide 12: Microstructural origin of the mechanical properties

2017 ◽  
Vol 89 ◽  
pp. 31-40 ◽  
Author(s):  
Thomas Stichel ◽  
Thomas Frick ◽  
Tobias Laumer ◽  
Felix Tenner ◽  
Tino Hausotte ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Round Robin ◽  
Polyamide 12

Fundamental investigation of part properties at accelerated beam speeds in the selective laser sintering process

2017 ◽  
Vol 23 (6) ◽  
pp. 1099-1106 ◽  
Author(s):  
Matthias Michael Lexow ◽  
Maximilian Drexler ◽  
Dietmar Drummer
Keyword(s):  
Mechanical Properties ◽  
Heating Rate ◽  
Energy Input ◽  
Selective Laser Sintering ◽  
Stable Process ◽  
Peak Height ◽  
Laser Sintering ◽  
Scanning Calorimetry ◽  
Content Type ◽  
The Core

Purpose Despite the recent progress in basic process understanding considering the selective laser sintering (SLS) of thermoplastics, several aspects of the mechanisms of the beam and powder interaction are not fully understood yet. Recent studies covered the correlation of mechanical properties and part density with the heating rate. The surface roughness of the test specimens was also considered but showed no distinct relation to the part mechanics. The purpose of this paper is to provide a new fundamental model for describing the decreasing mechanical properties with increasing beam speed. Design/methodology/approach While the dependence of mechanical properties with total energy input during exposure is well published, the correlation of the exposure speed with the degree of particle melt (DPM) is the subject of the present study. The DPM is accessible through differential scanning calorimetry measurements. Supporting the previously introduced method of the core-peak height, the interpretation via the core-peak area is proposed as a means to ascertain the melting behaviour for different processing conditions. Further support of the observations is given by x-ray computed tomography and microscopy which allows for a correlation with the respective porosity and inner structure of the parts. Findings The authors show a novel way of describing the decreasing mechanical properties with increasing speed of energy input by showing the dependence of the DPM on the heating rate during exposure. Practical implications The results offer an addition to the understanding considering the reliability and reproducibility of the SLS process. Originality/value The paper extends the existing models of the time-dependent material behaviour, which allows for the derivation of new efficient and stable process strategies.

Characterization and optimization of laser sintering copolyamide/polyether sulfone hot-melt adhesive mixtures

2019 ◽  
Vol 25 (3) ◽  
pp. 614-622
Author(s):  
Hui Zhang ◽  
Yanling Guo ◽  
Kaiyi Jiang ◽  
David Bourell ◽  
Jian Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Laser Energy ◽  
Laser Sintering ◽  
Polymer Mixture ◽  
Binding Mechanism ◽  
Content Type ◽  
Polyether Sulfone ◽  
Cent Increase ◽  
Mass Ratios ◽  
Hot Melt

PurposeA new kind of polymer mixture (co-PA-PES) was prepared in different mass ratios, by mixing polyether sulfone hot-melt adhesive (PES-HmA) and copolyamide B249 (PA-B249). This study aims to investigate its characteristics of laser sintering and get the optimal process parameters.Design/methodology/approachThe effect of mass ratio of co-PA-PES on thermal behavior was analyzed using a simultaneous thermal analyzer, and the density and mechanical properties of sintered parts were tested to evaluate the performance of the polymeric system. Scanning electron microscopy and Fourier transform infrared spectroscopy were performed to characterize the microstructure and binding mechanism of sintered co-PA-PES parts. Specifically, mechanical properties of the mixture with 20 Wt.% PA-B249 were optimized based on a design of experiment methodology, along with the restriction of maximum absorbable laser energy density.FindingsLiquid phase fusion was considered as the main sintering mechanism for co-PA-PES, and mechanical interlocking was the dominant binding mechanism. The effects of mass ratios of this material on the thermal properties, density and mechanical properties were obtained via data results. Additionally, compared to neat PES-HmA, co-20 Wt.% PA-PES showed a 71.7 per cent increase in tensile strength, 24.4 per cent increase in flexural strength and 102.1per cent increase in impact strength.Originality/valueThis paper proposed a new kind of polymer mixture as the feedstock for laser sintering with the advantages of low price and easy processing. The filler of PA-B249 effectively improved the performance of the polymer mixture, including but not limited to mechanical properties.

Study on the selective laser sintering of a low-isotacticity polypropylene powder

2016 ◽  
Vol 22 (4) ◽  
pp. 621-629 ◽  
Author(s):  
Wei Zhu ◽  
Chunze Yan ◽  
Yunsong Shi ◽  
Shifeng Wen ◽  
Changjun Han ◽  
...  
Keyword(s):  
Particle Size ◽  
Tensile Strength ◽  
Energy Density ◽  
Laser Energy ◽  
Selective Laser Sintering ◽  
Laser Energy Density ◽  
Content Type ◽  
Crystalline Polymers ◽  
Polyamide 12 ◽  
Degradation Temperature

Purpose Semi-crystalline polymers such as polyamide-12 can be used for selective laser sintering (SLS) to make near-fully dense plastic parts. At present, however, the types of semi-crystalline polymers suitable for SLS are critically limited. Therefore, the purpose of this paper is to investigate the processibility of a new kind of semi-crystalline polypropylene (PP) with low isotacticity for SLS process. Design/methodology/approach The SLS processibility of the PP powder, including particle size and shape, sintering window, degree of crystallinity and degradation temperature, was evaluated. Effects of the applied laser energy density on the surface micromorphology, density, tensile strength and thermal properties of SLS-built PP specimens were studied. Findings The results show that the PP powder has a nearly spherical shape, smooth surfaces, an appropriate average particle size of 63.6 μm, a broad sintering window of 21 oC and low crystalline degree of 30.4 per cent comparable to that of polyamide-12, a high degradation temperature of 381.8°C and low part bed temperature of 105°C, indicating a very good SLS processibility. The density and the tensile strength first increase with increasing laser energy density until they reach the maximum values of 0.831 g/cm3 and 19.9 MPa, respectively, at the laser energy density of 0.0458 J/mm2, and then decrease when the applied laser energy density continue to increase owing to the degradation of PP powders. The complex PP components have been manufactured by SLS using the optimum parameters, which are strong enough to be directly used as functional parts. Originality/value This paper provides a new knowledge for this field that low-isotacticity PPs exhibit good SLS processibility, therefore increasing material types and broadening the application of SLS technology.

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