scholarly journals Structure and Thermal Expansion of Cu−90 vol. % Graphite Composites

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7089
Author(s):  
Andrej Opálek ◽  
Štefan Emmer ◽  
Roman Čička ◽  
Naďa Beronská ◽  
Peter Oslanec ◽  
...  

Copper–graphite composites are promising functional materials exhibiting application potential in electrical equipment and heat exchangers, due to their lower expansion coefficient and high electrical and thermal conductivities. Here, copper–graphite composites with 10–90 vol. % graphite were prepared by hot isostatic pressing, and their microstructure and coefficient of thermal expansion (CTE) were experimentally examined. The CTE decreased with increasing graphite volume fraction, from 17.8 × 10−6 K−1 for HIPed pure copper to 4.9 × 10−6 K−1 for 90 vol. % graphite. In the HIPed pure copper, the presence of cuprous oxide was detected by SEM-EDS. In contrast, Cu–graphite composites contained only a very small amount of oxygen (OHN analysis). There was only one exception, the composite with 90 vol. % graphite contained around 1.8 wt. % water absorbed inside the structure. The internal stresses in the composites were released during the first heating cycle of the CTE measurement. The permanent prolongation and shape of CTE curves were strongly affected by composition. After the release of internal stresses, the CTE curves of composites did not change any further. Finally, the modified Schapery model, including anisotropy and the clustering of graphite, was used to model the dependence of CTE on graphite volume fraction. Modeling suggested that the clustering of graphite via van der Waals bonds (out of hexagonal plane) is the most critical parameter and significantly affects the microstructure and CTE of the Cu–graphite composites when more than 30 vol. % graphite is present.

Author(s):  
Aref Mehditabar ◽  
Seyed E Vahdat ◽  
Gholam-Hossein Rahimi

More than 70% of mechanical parts in a wide range of engineering fields fail by fatigue. In addition, centrifugal casting is identified as the most effective casting technique for production of high performance cylindrical parts. In this regard, the present work aims to investigate the fatigue behavior of series 3000 Al with addition of 26 wt% Cu produced through horizontal centrifugal casting method. Microstructure characterizations are precisely studied using scanning transmission electron microscopy and field emission scanning electron microscopy in conjunction with image analyzer software. Also, compressive behavior, hardness, coefficient of thermal expansion, and wear rate ( Wr) are measured applying Zwick Z100, Vickers hardness, DIL 805A/D, and pin-on-disc machines, respectively. The results indicate that the main intermetallic compound is Al2Cu-based particle, and a volume fraction of 31 vol.% is obtained. Besides, the compressive strength of 460 MPa, elastic modulus of 10.986 GPa, hardness of 152 HV, coefficient of thermal expansion of 1.7 × 10−5 1/°C, and wear resistance of 3.3 × 10−6 g/mm2 are measured. Finally, the four-point bending fatigue test is performed and the fatigue ratio of 0.109 at about 106 cycles to failure is obtained.


Author(s):  
Xiaolong Shi ◽  
Mohammad Kazem Hassanzadeh Aghdam ◽  
Reza Ansari

The objective of this work is to investigate the coefficient of thermal expansion of carbon nanotube reinforced aluminum matrix nanocomposites in which aluminum carbide (Al4C3) interphase formed due to chemical interaction between the carbon nanotube and aluminum matrix is included. To this end, the micromechanical finite element method along with a representative volume element, which incorporates, carbon nanotube, interphase, and aluminum matrix is employed. The emphasis is mainly placed on the effect of Al4C3 interphase on the coefficient of thermal expansion of aluminum nanocomposites with random microstructures. The effects of interphase thickness, carbon nanotube diameter, and volume fraction on the thermomechanical response of aluminum nanocomposite are discussed. The results reveal that the effect of Al4C3 interphase on the coefficient of thermal expansion of the aluminum nanocomposites becomes more significant with (i) increasing the coefficient of thermal expansion volume fraction, (ii) decreasing the coefficient of thermal expansion diameter, and (iii) increasing the interphase thickness. It is clearly observed that the coefficient of thermal expansion varies nonlinearly with the carbon nanotube diameter; however, it decreases linearly as the carbon nanotube volume fraction increases. Furthermore, the axial and transverse coefficient of thermal expansions of aligned continuous and discontinuous carbon nanotube-reinforced aluminum nanocomposites with Al4C3 interphase are predicted. Also, the presented finite element method results are compared with the available experiment in the literature, rule of mixture, and concentric cylinder model results.


2018 ◽  
Vol 30 (1) ◽  
pp. 32-44 ◽  
Author(s):  
Mohammad Javad Mahmoodi ◽  
Mohammad Kazem Hassanzadeh-Aghdam ◽  
Reza Ansari

In this study, a unit cell–based micromechanical approach is proposed to analyze the coefficient of thermal expansion of shape memory polymer nanocomposites containing SiO2 nanoparticles. The interphase region created due to the interaction between the SiO2 nanoparticles and shape memory polymer is modeled as the third phase in the nanocomposite representative volume element. The influences of the temperature, volume fraction, and diameter of the SiO2 nanoparticles on the thermal expansion behavior of shape memory polymer nanocomposite are explored. It is observed that the coefficient of thermal expansion of shape memory polymer nanocomposite decreases with the increase in the volume fraction up to 12%. Also, the results reveal that with the increase in temperature, the shape memory polymer nanocomposite coefficient of thermal expansion linearly increases. The role of interphase region on the thermal expansion response of the shape memory polymer nanocomposite is found to be very important. In the presence of interphase, the reduction in nanoparticle diameter leads to lower coefficient of thermal expansion for shape memory polymer nanocomposite, while the variation of nanoparticles diameter does not affect the coefficient of thermal expansion in the absence of interphase. Based on the simulation results, the shape memory polymer nanocomposite coefficient of thermal expansion decreases as the interphase thickness increases. In addition, the contribution of interphase coefficient of thermal expansion to the shape memory polymer nanocomposite coefficient of thermal expansion is more significant than that of interphase elastic modulus.


1967 ◽  
Vol 34 (4) ◽  
pp. 888-894 ◽  
Author(s):  
H. Tramposch

Equations were developed to describe the relaxation of the internal stresses of a wound reel of magnetic tape, with allowances for the effects of surface roughness between tape layers and unequal thermal expansion of hub and tape-layer body. Numerical examples obtained with the aid of a high-speed digital computer indicated that the surface roughness as well as the unequal thermal expansion of hub and tape-layer body greatly affect the internal stress distribution. Essentially independent of the surface roughness, a typical reel, when stored at 120 F after being wound at 70 F and when the coefficient of thermal expansion of the hub is three times the value of the tape material, will approach stress-free conditions about 80 percent earlier than when it is stored at the winding temperature.


2012 ◽  
Vol 620 ◽  
pp. 208-212
Author(s):  
Mohamd Nur Fuadi Pargi ◽  
Pei Leng Teh ◽  
Salmah Husseinsyah ◽  
Cheow Keat Yeoh

The effect of recycled copper filled epoxy composites on thermal, electrical and physical properties were investigated. The recycled copper was collected as a waste from the milling machine. The recycled copper filled epoxy composite was mixed using mechanical stirrer. The effect of volume fraction of recycled copper of the epoxy composites were studied based on the coefficient of thermal expansion (CTE), electrical conductivity hardness and density. Incorporation of recycled copper has decreased the CTE of the composites. The electrical conductivity, hardness and density of the composites increased with increasing of volume fraction and filler loading.


2020 ◽  
Vol 54 (13) ◽  
pp. 1761-1781
Author(s):  
SA Pottigar ◽  
B Santhosh ◽  
RG Nair ◽  
P Punith ◽  
PJ Guruprasad ◽  
...  

Three-dimensional braided composites with zero, negative and isotropic coefficient of thermal expansion are presented based on an analytical homogenization technique. The configuration of the braided composites is worked out considering the exact jamming condition leading to higher fiber volume fraction. A total of four configurations of three-dimensional-braided composite representative unit cells were analyzed. Among these, two arrangements are 4-axes and the other two are 5-axes. Special emphasis is given on the detailed description of the representative unit cells. Analysis reveals that a three-dimensional-braided composite configuration with thermoelastic isotropic properties having same coefficient of thermal expansion along x-, y-, and z-axes is achievable. As a special case, the homogenization model is used to predict, for the first time, a configuration of braided architecture and material leading to zero coefficient of thermal expansion along x-, y- and z-directions.


2011 ◽  
Vol 399-401 ◽  
pp. 315-319 ◽  
Author(s):  
Sheng Li Lv ◽  
Qing Na Zeng ◽  
Lei Jiang Yao ◽  
Xiao Yan Tong

The aim of this paper is to propose a microstructure modeling for prediction of thermal conductivity of plain weave C/SiC fibre bundles considering manufacturing flaws. Utilizing photomicrographs taken by scanning electron microscope (SEM), we established an accurate sub representative volume element (sub-RVE) model for carbon fiber bundles and RVE for the plain weave C/SiC composite with consideration of four classes of manufacturing porosity. The thermal expansion coefficient of carbon fibre bundles on axial and transverse coefficient of thermal expansion is calculated, respectively. Based on which thermal expansion coefficient of plain weave C/SiC is obtained with the value of 2.71×10-6 in-plain, which has a good correlation with experimental value. The influences of different manufacturing flaws on material’s thermal expansion coefficient are studied. The study shows that as the matrix porosity or crack volume fraction is increasing, thermal expansion coefficient of plain weave C/SiC is decreasing correspondingly while the speed gradually slows.


Author(s):  
Mohammad K Hassanzadeh-Aghdam

Understanding the structure–property relations for metal matrix nanocomposites reinforced with nanoparticles is a key factor for a reliable and optimal design of such new material systems. In the present study, coefficient of thermal expansion of silicon carbide (SiC) nanoparticle-reinforced aluminum (Al) matrix nanocomposites is predicted using a three-dimensional unit cell based micromechanical approach. The model takes into account the aluminum carbide (Al4C3) interphase region formed due to the reaction between SiC nanoparticles and surrounding Al matrix. The effects of some critical parameters, including volume fraction and diameter of SiC nanoparticles, interphase features such as geometry and material properties on the coefficient of thermal expansion of Al nanocomposite are extensively investigated. The obtained results clearly reveal the high influence of the interphase region on the coefficient of thermal expansion of Al nanocomposite. Based on the simulation results, the coefficient of thermal expansion of Al nanocomposite nonlinearly decreases with the increase in the interphase thickness or decreasing SiC nanoparticles diameter. Furthermore, the role of interphase in the thermal expansion behavior of Al nanocomposite becomes more prominent with the reduction in the nanoparticle diameter. Also, the coefficient of thermal expansion of Al nanocomposite linearly decreases as SiC nanoparticle volume fraction increases.


Author(s):  
Hervé Trumel ◽  
François Willot ◽  
Thomas Peyres ◽  
Maxime Biessy ◽  
François Rabette

The works deals with a macroscopically isotropic energetic material based on triamino-trinitrobenzene (TATB) crystals bonded with a small volume fraction of a thermoplastic polymer. This material is shown experimentally to display an irreversible thermal expansion behavior characterized by dilatancy and variations of its thermal expansion coefficient when heated or cooled outside a narrow reversibility temperature range. The analysis of cooling results suggests the existence of residual stresses in the initial state, attributed to the manufacturing process. Microstructure-level FFT computations including the very strong anisotropic thermoelastic TATB crystal response and temperature-dependent binder plasticity, show that strong internal stresses develop in the disoriented crystals under thermal load, either heating or cooling. Upon cooling, binder plastic yielding in hindered, thus promoting essentially brittle microcracking, while it is favored upon heating. Despite its low volume fraction, the role of the binder is essential, its plastic yielding causing stress redistribution and residual stresses upon cooling back to ambient.


2008 ◽  
Vol 22 (31n32) ◽  
pp. 6167-6172 ◽  
Author(s):  
EUSUN YU ◽  
JEONG-YUN SUN ◽  
HEE-SUK CHUNG ◽  
KYU HWAN OH

Computational simulations on the thermal analysis of metal matrix composite (MMC) composed of Al and SiC were performed in extended areas of SiC volume fraction. Due to the experimental limitations, only the narrow range of SiC volume fraction has been examined. Through the simulation, which enables current experimental situation to extend, we attempted to explore the dependencies of thermal and mechanical properties on changing the value of volume fraction ( V f ). To calculate the coefficient of thermal expansion (CTE), variables with temperature and V f were given in a range from 25°C to 100°C and 0 to 100%, respectively. We obtained quantitative results including CTE as a function of V f , which are in a good agreement with previous experimental reports. Furthermore, the stress analysis about thermally expanded MMC was performed. At low volume fraction of SiC , the thermal expansion caused the tensile stress at Al near the interface. However, as the volume fraction of SiC was increased, the stress turned to be compressive, it's because the linked SiC particles contracted the expansion of Al . The MMC of Al matrix face centered cubic site SiC particles has more stress evolutions than the MMC of Al matrix simple cubic site SiC particles at same volume fraction.


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