Tailoring anisotropic thermal conductivity by varying filler particle organization in nickel-polydimethylsiloxane composites

2019 ◽  
Vol 53 (18) ◽  
pp. 2569-2577
Author(s):  
Peiying J Tsai ◽  
Souvik Pal ◽  
Suvojit Ghosh ◽  
Ishwar K Puri
Keyword(s):  
Thermal Conductivity ◽  
Additive Manufacturing ◽  
Volume Fraction ◽  
Filler Particle ◽  
Material Design ◽  
Interparticle Spacing ◽  
Element Analysis ◽  
Anisotropic Thermal Conductivity ◽  
Transverse Conductivity ◽  
Filler Particles

Anisotropic properties can be imparted to composite materials by arranging filler particles along specific directions inside the polymer matrix. These anisotropic patterns can be produced through dynamic field-assisted assembly of the filler particles during additive manufacturing. Using finite element analysis, we explore how chainlike arrangements of nickel particles embedded in a polydimethylsiloxane matrix modify bulk thermal conductivities in the axial and transverse directions. The axial conductivity increases up to nine times of the matrix conductivity with increasing filler volume fraction. While the axial conductivity decreases with increasing interparticle spacing, the transverse conductivity is uninfluenced. When particles within a chain are arranged in a zigzag pattern, increasing the interparticle zigzag angle decreases axial conductivity but increases transverse conductivity. As that angle increases to ∼55 º, the axial conductivity approaches a minimum, while the transverse conductivity approaches its maximum. An empirical model that includes effects of interparticle spacing and zigzag angle to predict the anisotropic thermal conductivity of a composite containing particle chains is presented. These results are relevant for the material design of particulate-reinforced polymer composites for advanced field-assisted additive manufacturing strategies.

scholarly journals An effective thermal conductivity and thermomechanical homogenization scheme for a multiscale Nb3Sn filaments

2021 ◽  
Vol 10 (1) ◽  
pp. 187-200
Author(s):  
Xiaoyu Zhao ◽  
Guannan Wang ◽  
Qiang Chen ◽  
Libin Duan ◽  
Wenqiong Tu
Keyword(s):  
Volume Fraction ◽  
Material Design ◽  
Axial Direction ◽  
High Heat ◽  
Thermomechanical Properties ◽  
Homogenization Theory ◽  
High Heat Flux ◽  
Element Analysis ◽  
Hierarchical Microstructure ◽  
Thermal Conductivities

Abstract A comprehensive study of the multiscale homogenized thermal conductivities and thermomechanical properties is conducted towards the filament groups of European Advanced Superconductors (EAS) strand via the recently proposed Multiphysics Locally Exact Homogenization Theory (LEHT). The filament groups have a distinctive two-level hierarchical microstructure with a repeating pattern perpendicular to the axial direction of Nb3Sn filament. The Nb3Sn filaments are processed in a very high temperature between 600 and 700°C, while its operation temperature is extremely low, −269°C. Meanwhile, Nb3Sn may experience high heat flux due to low resistivity of Nb3Sn in the normal state. The intrinsic hierarchical microstructure of Nb3Sn filament groups and Multiphysics loading conditions make LEHT an ideal candidate to conduct the homogenized thermal conductivities and thermomechanical analysis. First, a comparison with a finite element analysis is conducted to validate effectiveness of Multiphysics LEHT and good agreement is obtained for the homogenized thermal conductivities and mechanical and thermal expansion properties. Then, the Multiphysics LEHT is applied to systematically investigate the effects of volume fraction and temperature on homogenized thermal conductivities and thermomechanical properties of Nb3Sn filaments at the microscale and mesoscale. Those homogenized properties provide a full picture for researchers or engineers to understand the Nb3Sn homogenized properties and will further facilitate the material design and application.

On Thermal Interface Materials With Polydisperse Fillers: Packing Algorithm and Effective Properties

2018 ◽  
Author(s):  
Piyas Chowdhury ◽  
Kamal Sikka ◽  
Anuja De Silva ◽  
Indira Seshadri
Keyword(s):  
Thermal Conductivity ◽  
Elastic Modulus ◽  
Volume Fraction ◽  
Effective Properties ◽  
Material Design ◽  
High Volume ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Packing Algorithm ◽  
Interface Materials

Thermal interface materials (TIMs), which transmit heat from semiconductor chips, are indispensable in today’s microelectronic devices. Designing superior TIMs for increasingly demanding integration requirements, especially for server-level hardware with high power density chips, remains a particularly coveted yet challenging objective. This is because achieving desired degrees of thermal-mechanical attributes (e.g. high thermal conductivity, low elastic modulus, low viscosity) poses contradictory challenges. For instance, embedding thermally conductive fillers (e.g. metallic particles) into a compliant yet considerably less conductive matrix (e.g. polymer) enhances heat transmission, however at the expense of overall compliance. This leads to extensive trial-and-error based empirical approaches for optimal material design. Specifically, high volume fraction filler loading, role of filler size distribution, mixing of various filler types are some outstanding issues that need further clarification. To that end, we first forward a generic packing algorithm with ability to simulate a variety of filler types and distributions. Secondly, by modeling the physics of heat/force flux, we predict effective thermal conductivity, elastic modulus and viscosity for various packing cases.

scholarly journals Magnetic Field Effect on Thermal, Dielectric, and Viscous Properties of a Transformer Oil-Based Magnetic Nanofluid

Energies ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4532 ◽  
Author(s):  
Michal Rajnak ◽  
Zan Wu ◽  
Bystrik Dolnik ◽  
Katarina Paulovicova ◽  
Jana Tothova ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Thermal Conductivity ◽  
Volume Fraction ◽  
Effective Medium Theory ◽  
Transformer Oil ◽  
Dielectric Anisotropy ◽  
Magnetic Nanofluid ◽  
Conductivity Sensor ◽  
Anisotropic Thermal Conductivity ◽  
Transformer Oils

Progress in electrical engineering puts a greater demand on the cooling and insulating properties of liquid media, such as transformer oils. To enhance their performance, researchers develop various nanofluids based on transformer oils. In this study, we focus on novel commercial transformer oil and a magnetic nanofluid containing iron oxide nanoparticles. Three key properties are experimentally investigated in this paper. Thermal conductivity was studied by a transient plane source method dependent on the magnetic volume fraction and external magnetic field. It is shown that the classical effective medium theory, such as the Maxwell model, fails to explain the obtained results. We highlight the importance of the magnetic field distribution and the location of the thermal conductivity sensor in the analysis of the anisotropic thermal conductivity. Dielectric permittivity of the magnetic nanofluid, dependent on electric field frequency and magnetic volume fraction, was measured by an LCR meter. The measurements were carried out in thin sample cells yielding unusual magneto-dielectric anisotropy, which was dependent on the magnetic volume fraction. Finally, the viscosity of the studied magnetic fluid was experimentally studied by means of a rheometer with a magneto-rheological device. The measurements proved the magneto-viscous effect, which intensifies with increasing magnetic volume fraction.

Numerical Analysis of the Transverse Thermal Conductivity of Composites With Imperfect Interfaces

2003 ◽  
Vol 125 (3) ◽  
pp. 389-393 ◽  
Author(s):  
Samuel Graham ◽  
David L. McDowell
Keyword(s):  
Thermal Conductivity ◽  
Volume Fraction ◽  
Ceramic Composites ◽  
Reinforced Composites ◽  
Continuous Fiber ◽  
Fiber Volume ◽  
Element Analysis ◽  
Imperfect Interfaces ◽  
Transverse Thermal Conductivity ◽  
Johnson Model

Estimation of the transverse thermal conductivity of continuous fiber reinforced composites containing a random fiber distribution with imperfect interfaces was performed using finite element analysis. FEA results were compared with the classical solution of Hasselman and Johnson to determine limits of applicability. The results show that the Hasselman and Johnson model predicts the effective thermal conductivity within 3 percent of the numerical estimates for interfacial conductance values of 1×10−2−1×103W/m2K, fiber-matrix conductivity ratios between 1 and 100, and fiber volume fractions up to 50 percent which are properties typical of ceramic composites. The results show that the applicability of the classical dilute concentration model can not be determined by constituent volume fraction, but by the degree of interaction between the microstructural heterogeneities.

Effect of Fiber Volume Fraction on Thermal Conductivity of a Woven-Mat Composite Lamina

2005 ◽  
Author(s):  
Hossein Golestanian
Keyword(s):  
Thermal Conductivity ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Epoxy Composite ◽  
Fiber Volume ◽  
Element Analysis ◽  
Fiber Mats ◽  
The Common ◽  
Thermal Conductivities

Models are presented for the determination of thermal conductivity of a composite lamina with woven fiber mats. In analyzing the cure cycle of a composite part, the common practice has been to use weight-averaged thermal properties. The limitation of this approach becomes apparent when one finds that thermal conductivity calculated for fiberglass/epoxy composite is very close to thermal conductivity of carbon/epoxy composite. This happens for composite parts with the same fiber volume fraction. In weight-average formulations the effect of fiber thermal conductivity is overshadowed by the density of the constituents. To overcome this problem, one needs to take another approach. In this investigation finite element analysis is performed to determine thermal conductivities of fiberglass/epoxy and carbon/epoxy composite lamina. The resulting thermal conductivities are different for the two composite types. These results make more physical sense since thermal conductivity of carbon fiber mat is much higher than that of fiberglass mat.

Thermal conductivity enhancement of polyimide films filled with BN and AlN fillers

2018 ◽  
Vol 31 (8) ◽  
pp. 959-968 ◽  
Author(s):  
Xinyu Ma ◽  
Lizhu Liu ◽  
Xiaorui Zhang ◽  
Tong Lv
Keyword(s):  
Thermal Conductivity ◽  
Surface Modification ◽  
Composite Film ◽  
Volume Fraction ◽  
Conductive Filler ◽  
Breakdown Field ◽  
Silane Coupling Agents ◽  
Conductivity Enhancement ◽  
Silane Coupling ◽  
Filler Particles

A series of polyimide (PI) composite films were prepared using PI as matrix and boron nitride (BN) and aluminum nitride (AlN) as the doped phases. The modification of the thermal conductive filler particles was characterized by Fourier transform infrared (FTIR). The results showed that the silane coupling agent KH550 was successfully coated on the surface of BN and AlN. X-ray photoelectron spectrometer characterization was used to further prove that silane coupling agents were successfully attached to BN and AlN surfaces, forming a new chemical bond. Scanning electron microscope (SEM) was used to analyze the dispersion of filler particles in the matrix. It was found that agglomeration phenomenon occurred when the content of BN particles were high, but this problem was improved after the surface modification of BN. The breakdown field strength and volume resistivity of PI/BN composite film increased first and then decreased with the increase of BN content and reached the maximum when the volume fraction of BN was 5%, which was 191.53 kV/mm and 8.832 × 1013 Ω·m, respectively. When the BN content was 9 vol%, the thermal conductivity of the PI/BN composite film was 0.496 W/(m·K), which was 1.4 times larger than that of the pure PI film. The thermal conductivity of the PI/BN/AlN composite film at the BN and AlN contents of 5 vol% and 1 vol%, respectively, is 0.144 W/(m·K) higher than that of 7 vol% PI/BN. It indicated that the synergistic effect of the composite fillers played a significant role, and at the same time, under the premise of ensuring higher thermal conductivity, the amount of thermally conductive particles could be reduced to some extent. After the surface modification of the filler particles, the properties of the composite film showed the same trend compared with the unmodified one, while the only difference was that there was a certain increase in the numerical value.

The Thermal Conductivity Analysis of Sip/Al Base Composites

2011 ◽  
Vol 675-677 ◽  
pp. 775-778
Author(s):  
Ming Li ◽  
Hai Hao ◽  
Ying De Song ◽  
Xing Guo Zhang
Keyword(s):  
Thermal Conductivity ◽  
Volume Fraction ◽  
The Other ◽  
Low Density ◽  
Working Ability ◽  
Element Analysis ◽  
Low Thermal Expansion ◽  
The Finite Element Analysis ◽  
Si Content ◽  
Aluminum Base

Aluminum base composites with particles reinforced have high thermal conductivity, low thermal expansion coefficient, low density, and excellent working ability. On one hand the Sip/Al composites are prepared by pressure-less infiltration in experiments and take advantage of the finite element analysis to establish the models of Sip/Al composites. On the other hand, the Sip/Al composites morphology, the particles size, the volume fraction and the ratio between different Si particles have been discussed in the experiments. In experiments how they affect the thermal conductivity of the composites also has been explained. The thermal conductivity of Sip/Al composites is around 100 W/(m.k) at 50°C. When the Si volume fraction is definite, the thermal conductivity of the composites is little affected by the morphology, the size and the ratio between different Si particles. The study also showed that with the element Si content increasing, the thermal conductivity will decrease.

Effect of the Carbon Nanotube Distribution on the Thermal Conductivity of Composite Materials

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Iman Eslami Afrooz ◽  
Andreas Öchsner
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Finite Element Analysis ◽  
Composite Materials ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Fiber Volume ◽  
Element Analysis ◽  
The Matrix ◽  
Good Agreement

Finite element analysis has been employed to investigate the effect of carbon nanotubes (CNTs) distribution on the thermal conductivity of composite materials. Several kinds of representative volume elements (RVEs) employed in this study are made by assuming that unidirectional CNTs are randomly distributed in a polymer matrix. It is also assumed that each set of RVEs contains a constant fiber volume fraction and aspect ratio. Results show that randomness—the way in which fibers are distributed inside the matrix—has a significant effect on the thermal conductivity of CNT composites. Results of this study were compared using the analytical Xue and Nan model and good agreement was observed.

The behaviour of aluminium matrix composites under thermal stresses

2016 ◽  
Vol 23 (1) ◽  
pp. 1-20 ◽  
Author(s):  
Khushbu Dash ◽  
Suvin Sukumaran ◽  
Bankim C. Ray
Keyword(s):  
Thermal Conductivity ◽  
Thermal Cycling ◽  
Thermal Fatigue ◽  
Thermal Stresses ◽  
Volume Fraction ◽  
Coefficient Of Thermal Expansion ◽  
Interparticle Spacing ◽  
Aluminium Matrix ◽  
Matrix Composites ◽  
Aluminium Matrix Composites

AbstractThe present review work elaborates the behaviour of aluminium matrix composites (AMCs) under various kinds of thermal stresses. AMCs find a number of applications such as automobile brake systems, cryostats, microprocessor lids, space structures, rocket turbine housing, and fan exit guide vanes in gas turbine engines. These applications require operation at varying temperature conditions ranging from high to cryogenic temperatures. The main objective of this paper was to understand the behaviour of AMCs during thermal cycling, under induced thermal stresses and thermal fatigue. It also focuses on the various thermal properties of AMCs such as thermal conductivity and coefficient of thermal expansion (CTE). CTE mismatch between the reinforcement phase and the aluminium matrix results in the generation of residual thermal stress by virtue of fabrication. These thermal stresses increase with increasing volume fraction of the reinforcement and decrease with increasing interparticle spacing. Thermal cycling enhances plasticity at the interface, resulting in deformation at stresses much lower than their yield stress. Low and stable CTE can be achieved by increasing the volume fraction of the reinforcement. The thermal fatigue resistance of AMC can be increased by increasing the reinforcement volume fraction and decreasing the particle size. The thermal conductivity of AMCs decreases with increase in reinforcement volume fraction and porosity.

Sign in / Sign up

Export Citation Format

Share Document