scholarly journals Influence of packing density and fillers on thermal conductivity of polymer powders for additive manufacturing

2021 ◽  
Author(s):  
Francesco Sillani ◽  
Fabian de Gasparo ◽  
Manfred Schmid ◽  
Konrad Wegener
Keyword(s):  
Thermal Conductivity ◽  
Additive Manufacturing ◽  
Packing Density ◽  
Heating System ◽  
Neat Polymer ◽  
Additional Tool ◽  
Powder Packing ◽  
Inhomogeneous Temperature ◽  
Thermal Phenomena ◽  
Polymer Powders

AbstractAdditive manufacturing of polymer powders is nowadays an industrial production technology. Complex thermal phenomena occur during processing, mainly related to the interaction dynamics among laser, powder, and heating system, and also to the subsequent cool-down phase from the melt to the parts. Thermal conductivity of the powder is a key property for material processing, since an inhomogeneous temperature field in the powder cake leads to uneven part properties and can strongly limit productivity because only a smaller portion of the build chamber can be used. Nevertheless, little is known about the relationship between thermal conductivity, packing density, and presence of fillers, which are used to enhance specific properties such as high temperature resistance or stiffness. The development and consequent validation of a device capable of measuring thermal conductivity as a function of powder packing density are then extremely important, providing an additional tool to characterize powders during the development process of new materials for PBF of polymers. The results showed a positive correlation between packing density and thermal conductivity for some commercially available materials, with an increase of the latter of about 10 to 40% with an increase of the packing density from 0 to 100%. Problems arose in trying to replicate the compaction state of the powder, since the same amount of taps led to a different packing density, but this is a known problem of measuring free-flowing powders such as the ones used for additive manufacturing. Regarding fillers, an increase of about 40 to 70% of thermal conductivity when inorganic fillers such as carbon fibers are added to the neat polymer was observed, and the expected behavior following the rule of mixture was only partially observed.

Optimization of tape width and powder packing density in the powder-in-tube processing of (Bi,Pb)-2223 tapes

1998 ◽  
Vol 309 (3-4) ◽  
pp. 203-207 ◽  
Author(s):  
R.P. Aloysius ◽  
A. Sobha ◽  
P. Guruswamy ◽  
K.G.K. Warrier ◽  
U. Syamaprasad
Keyword(s):  
Packing Density ◽  
Powder Packing ◽  
Powder In Tube

Thermal Transport in Nanocrystalline Materials

2005 ◽  
Author(s):  
Zhanrong Zhong ◽  
Xinwei Wang
Keyword(s):  
Thermal Conductivity ◽  
Specific Heat ◽  
Thermal Transport ◽  
Nanocrystalline Materials ◽  
Large Scale ◽  
Md Simulation ◽  
Fundamental Physics ◽  
Grain Sizes ◽  
Simulation Results ◽  
Thermal Phenomena

In this work, thermal transport in nanocrystalline materials is studied using large-scale equilibrium molecular dynamics (MD) simulation. Nanocrystalline materials with different grain sizes are studied to explore how and to what extent the size of nanograins affects the thermal conductivity and specific heat. Substantial thermal conductivity reduction is observed and the reduction is stronger for nanocrystalline materials with smaller grains. On the other hand, the specific heat of nanocrystalline materials shows little change with the grain size. The simulation results are compared with the thermal transport in individual nanograins based on MD simulation. Further discussions are provided to explain the fundamental physics behind the observed thermal phenomena in this work.

Thermal conductivity of metal powders for powder bed additive manufacturing

2018 ◽  
Vol 21 ◽  
pp. 201-208 ◽  
Author(s):  
Lien Chin Wei ◽  
Lili E. Ehrlich ◽  
Matthew J. Powell-Palm ◽  
Colt Montgomery ◽  
Jack Beuth ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Additive Manufacturing ◽  
Metal Powders ◽  
Powder Bed

A NOVEL, SCALABLE PRODUCTION OF MULTIFUNCTIONAL NANOCOMPOSITE POLYMER FILAMENTS FOR ADDITIVE MANUFACTURING

2021 ◽  
Author(s):  
MIA CARROLA ◽  
AMIR ASADI
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Additive Manufacturing ◽  
Aqueous Suspension ◽  
Manufacturing Method ◽  
Nanocomposite Polymer ◽  
Water As Solvent ◽  
Materials Used ◽  
Scalable Production

Though a revolutionary process, additive manufacturing (AM) has left more to be desired from printed parts, specifically, improved interlayer strength and minimal defects such as porosity. To overcome these common issues, nanocomposites have become one of the most popular materials used in AM, with various nanoparticles used to achieve a variety of characteristics. The use of these technologies together allows for both to synergistically enhance the final printed parts by improving the process and products simultaneously. Here, we introduce a novel, scalable technique to coat ABS pellets with cellulose nanocrystal (CNC) bonded carbon nanotubes (CNT), to improve the adhesion between layers as well as the mechanical properties of printed parts. An aqueous suspension of CNT-CNC is used to coat ABS pellets before they are dried and extruded into filament for printing. The filament produced using this manufacturing method showed an increase in tensile and interlayer strength as well as improved thermal conductivity. This process uses water as solvent and pristine nanoparticles without the need for any functionalization or surfactants, promoting its scalability. This process has the potential to be used with various polymers and nanoparticles, which allows the materials to be specifically tailored to the end application, (i.e. strength, conductivity, antibacterial, etc.). These nanocomposite filaments have the potential to revolutionize the way that additive manufacturing is utilized in a variety of industries.

scholarly journals Analytical Modeling of In-Process Temperature in Powder Bed Additive Manufacturing Considering Laser Power Absorption, Latent Heat, Scanning Strategy, and Powder Packing

Materials ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 808 ◽  
Author(s):  
Jinqiang Ning ◽  
Daniel Sievers ◽  
Hamid Garmestani ◽  
Steven Liang
Keyword(s):  
Additive Manufacturing ◽  
Computational Efficiency ◽  
Molten Pool ◽  
Laser Power ◽  
Analytical Modeling ◽  
Single Track ◽  
Scanning Strategy ◽  
Powder Bed ◽  
Powder Packing ◽  
High Computational Efficiency

Temperature distribution gradient in metal powder bed additive manufacturing (MPBAM) directly controls the mechanical properties and dimensional accuracy of the build part. Experimental approach and numerical modeling approach for temperature in MPBAM are limited by the restricted accessibility and high computational cost, respectively. Analytical models were reported with high computational efficiency, but the developed models employed a moving coordinate and semi-infinite medium assumption, which neglected the part dimensions, and thus reduced their usefulness in real applications. This paper investigates the in-process temperature in MPBAM through analytical modeling using a stationary coordinate with an origin at the part boundary (absolute coordinate). Analytical solutions are developed for temperature prediction of single-track scan and multi-track scans considering scanning strategy. Inconel 625 is chosen to test the proposed model. Laser power absorption is inversely identified with the prediction of molten pool dimensions. Latent heat is considered using the heat integration method. The molten pool evolution is investigated with respect to scanning time. The stabilized temperatures in the single-track scan and bidirectional scans are predicted under various process conditions. Close agreements are observed upon validation to the experimental values in the literature. Furthermore, a positive relationship between molten pool dimensions and powder packing porosity was observed through sensitivity analysis. With benefits of the absolute coordinate, and high computational efficiency, the presented model can predict the temperature for a dimensional part during MPBAM, which can be used to further investigate residual stress and distortion in real applications.

On the suitability of induction heating system for metal additive manufacturing

2020 ◽  
Vol 235 (1-2) ◽  
pp. 219-229 ◽  
Author(s):  
Gourav K Sharma ◽  
Piyush Pant ◽  
Prashant K Jain ◽  
Pavan K Kankar ◽  
Puneet Tandon
Keyword(s):  
Energy Source ◽  
Additive Manufacturing ◽  
Induction Heating ◽  
Low Cost ◽  
Three Dimensional ◽  
Experimental System ◽  
Heating System ◽  
Industrial Applications ◽  
Metallic Materials ◽  
Semi Solid

Induction heating is a non-contact-based energy source that has the potential to quickly melt the metal and become the alternate energy source that can be used for additive manufacturing. At present, induction heating is widely used in various industrial applications such as melting, preheating, heat treatment, welding, and brazing. The potential of this source has not been explored in the additive manufacturing domain. However, the use of induction heating in additive manufacturing could lead to low-cost part fabrication as compared to other energy sources such as laser or electron beam. Therefore, this study explores the feasibility of this energy source in additive manufacturing for fabricating parts of metallic materials. An experimental system has been developed by modifying an existing delta three-dimensional printer. An induction heater coil has been incorporated to extruder head for semi-solid processing of the metal alloy. In order to test the viability of the developed system, aluminium material in the filament form has been processed. Obtained results have shown that the induction heating–based energy source is capable of processing metallic materials having a melting point up to 1000° C. The continuous extrusion of the material has been achieved by controlling the extruder temperature using a proportional integral derivative–based controller and k-type thermocouple. The study also discusses various issues and challenges that occurred during the melting of metal with induction heating. The outcomes of this study may be a breakthrough in the area of metal-based additive manufacturing.

Effects of Various Parameters on Nanofluid Thermal Conductivity

2006 ◽  
Vol 129 (5) ◽  
pp. 617-623 ◽  
Author(s):  
Seok Pil Jang ◽  
Stephen U. S. Choi
Keyword(s):  
Thermal Conductivity ◽  
Thermal Behavior ◽  
Volume Fraction ◽  
Heat Transfer Fluids ◽  
New Concepts ◽  
Model Predictions ◽  
Simplifying Assumptions ◽  
Thermal Phenomena ◽  
First Time ◽  
Good Agreement

The addition of a small amount of nanoparticles in heat transfer fluids results in the new thermal phenomena of nanofluids (nanoparticle-fluid suspensions) reported in many investigations. However, traditional conductivity theories such as the Maxwell or other macroscale approaches cannot explain the thermal behavior of nanofluids. Recently, Jang and Choi proposed and modeled for the first time the Brownian-motion-induced nanoconvection as a key nanoscale mechanism governing the thermal behavior of nanofluids, but did not clearly explain this and other new concepts used in the model. This paper explains in detail the new concepts and simplifying assumptions and reports the effects of various parameters such as the ratio of the thermal conductivity of nanoparticles to that of a base fluid, volume fraction, nanoparticle size, and temperature on the effective thermal conductivity of nanofluids. Comparison of model predictions with published experimental data shows good agreement for nanofluids containing oxide, metallic, and carbon nanotubes.

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