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.

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.

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.

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.

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.

The effect of different build orientations on the consolidation, tensile and fracture toughness properties of direct metal laser sintering Ti-6Al-4V

2018 ◽  
Vol 24 (2) ◽  
pp. 276-284 ◽  
Author(s):  
Hamza Hassn Alsalla ◽  
Christopher Smith ◽  
Liang Hao
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Laser Sintering ◽  
Full Density ◽  
Full Detail ◽  
Original Research ◽  
Metal Powders ◽  
Direct Metal Laser Sintering ◽  
Cast Material ◽  
Content Type

Purpose The purpose of this paper is to study new process parameters which were selected to achieve the full density of Ti-6Al-4V samples in different building orientations and investigate fracture toughness property and its relation to the microstructure, an area which has not previously been reported in full detail and which may offer information to a designer. Direct metal laser sintering (DMLS) is an additive manufacturing technique that directly manufactures three-dimensional parts, layer-by-layer, to scan and melt metal powders for aerospace applications. Design/methodology/approach Hardness and tensile tests were carried out to evaluate the effect of consolidation on the mechanical performance of specimens made at three different building directions. Optical and electron microscopy were used to characterise the microstructure of the DMLS specimens and their effects on the fractures and mechanical properties. Findings It was found that the built samples have an excellent density at 4.5 g/cm, and the sample surfaces parallel to the building direction are rougher than the perpendicular surfaces. The fracture toughness result was higher than that of the cast material for the same alloy and higher than the Ti-6Al-4V parts fabricated by electron beam melting. This results in the superior mechanical properties of DMLS, while slightly lower in the zy direction owing to cracks, porosity and surface finish. Research limitations/implications The tensile strength was found to be higher than the wrought material, and the samples exhibited brittle fractures owing to the martensitic phase, which is caused by a high temperature gradient, and the mechanical properties change with the change in the microstructures at different building directions. Originality/value This paper contains original research.

Study on laser sintering of pine/co-PES composites and the investment casting process

2019 ◽  
Vol 25 (8) ◽  
pp. 1349-1358 ◽  
Author(s):  
Hui Zhang ◽  
David Bourell ◽  
Yanling Guo ◽  
Xiaodong Zhang ◽  
Yu Zhuang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Process Parameters ◽  
Investment Casting ◽  
Laser Sintering ◽  
Processing Temperature ◽  
Post Processing ◽  
Advanced Technique ◽  
Content Type ◽  
Structural Patterns ◽  
Complex Structural

Purpose A pine/co-PES composite (PCPES composite) was proposed as the feedstock for powder bed fusion (laser sintering, LS). This paper aims to provide some necessary experimental data and the theoretical foundation for LS of pine/co-PES, especially for the application of using the laser-sintered pine/co-PES parts as complex structural patterns in investment casting. Design/methodology/approach The PCPES composites with different pine loadings were mixed mechanically. The composite’s preheating temperature and processing temperature during LS were determined experimentally based on the material’s thermal behavior. The effects of pine powder on the binding mechanism of PCPES composites were discussed through analyzing the microstructure of the laser-sintered parts’. Mechanical properties and dimensional precision of laser-sintered PCPES parts in different pine loadings were tested, and the parts’ mechanical properties were strengthened by wax-infiltration post-processing. The influence extents of process parameters on the mechanical properties of laser-sintered 20 Wt.% pine/co-PES parts were investigated using a 1/2 fractional factorials experiment. Findings 20 Wt.% pine/co-PES is considered to be a promising wood-plastic composite for laser sintering. The relationship between mechanical strength of its laser-sintered parts and process parameters was built up using mathematical formulas. Experimental results show density, tensile strength, flexural strength and surface roughness of laser-sintered 20 Wt.% pine/co-PES parts are improved by 72.7-75.0%, 21.9-111.3%, 26.8-86.2%, 27.0-29.1% after post-process infiltration with a wax. A promising application of the wax-infiltrated laser-sintered parts is for investment casting cores and patterns. Research limitations/implications The proper process parameters and forming properties of laser-sintered parts are limited to the results of laser sintering experiments carried on using AFS 360 rapid prototyping device. Originality/value This investigation not only provides a new feedstock for laser sintering with the advantages of low cost and fabricability but also uses an advanced technique to produce personalized wood-plastic parts efficiently. Mathematical models between mechanical properties of laser-sintered PCPES parts and LS process parameters will guide the further LS experiments using the 20 Wt.% pine/co-PES composite. Besides, the laser-sintered PCPES parts after wax-infiltration post-processing are promising as complex structural patterns for use in investment casting.

scholarly journals Analysis and Optimization of Mechanical Properties of Laser-Sintered Cellulose/PLA Mixture

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 750
Author(s):  
Hui Zhang ◽  
David L. Bourell ◽  
Yanling Guo
Keyword(s):  
Mechanical Properties ◽  
Process Parameters ◽  
Laser Energy ◽  
Design Method ◽  
Laser Sintering ◽  
Post Processing ◽  
Annealing Temperatures ◽  
Scan Speed ◽  
Full Factorial

This studied aimed at improving the mechanical properties for a new biopolymer feedstock using laser-sintering technology, especially when its laser-sintered parts are intended to be applied in the industrial and medical fields. Process parameter optimization and thermal post-processing are two approaches proposed in this work to improve the mechanical properties of laser-sintered 10 wt % cellulose-polylactic acid (10%-CPLA) parts. Laser-sintering experiments using 23 full factorial design method were conducted to assess the effects of process parameters on parts’ mechanical properties. A simulation of laser-energy distribution was carried out using Matlab to evaluate the experimental results. The characterization of mechanical properties, crystallinity, microstructure, and porosity of laser-sintered 10%-CPLA parts after thermal post-processing of different annealing temperatures was performed to analyze the influence of thermal post-processing on part properties. Image analysis of fracture surfaces was used to obtain the porosity of laser-sintered 10%-CPLA parts. Results showed that the optimized process parameters for mechanical properties of laser-sintered 10%-CPLA parts were laser power 27 W, scan speed 1600 mm/s, and scan spacing 0.1 mm. Thermal post-processing at 110 °C produced best properties for laser-sintered 10%-CPLA parts.

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