Analysis of Mechanical characteristics of Aluminium Nanocomposites using Multiwall carbon nano tubes

Home»Analysis of Mechanical characteristics of Aluminium Nanocomposites using Multiwall carbon nano tubes

Abstract:-

Aluminium and its alloys are increasingly being used in different fields like automobile industries, aerospace industries and many other applications due to its lightweight and specific strength properties. Tensile strength, impact resistance and wear resistance are the weaker sides of aluminium hindering its widespread applications in manufacturing sector. An attempt has been made for improving these properties by introducing carbon nanotubes with aluminium metal to form a Nanocomposite. Aluminium is used as the metal matrix with Multi-walled carbon nanotube (MWCNT) as the reinforcing element. Mechanical properties of the composite, as well as a comparison with properties of the metal, is carried out and machining parameters for the industrial sector is also attempted in the study.

Introduction:-

Aluminium is extensively used nowadays in manufacturing IC engine components, gears, pipe fittings, bushes, bearings, pumps etc. replacing the conventional ferrous alloys. Composites came into existence when a need to combine the properties of different combination of materials occurred. A reinforced phase, in the form of fibre, powder, sheets or particles; when infiltrated or dispersed in the matrix phase, that could be in slurry, porous or foam structure; a new material with better properties than the parent phases is obtained with a proper choice of manufacturing process and processing parameters. Nano composites are a newer kind of composites where the reinforcing phase has its one, two or three dimensions at Nano level (10-9). In the study, the matrix phase is
Aluminium and the reinforcement is multi-wall carbon nanotube. The grade of Aluminium alloy used is Aluminium LM25. Nano composites differ from conventional composites because of its high surface-to-volume ratio of its reinforcing phase. Macro-scale properties can be substantially increased with addition of a minuscule nano-scale reinforcement. Cast aluminium alloys yielding cost-effective products when infiltrated with a small amount (0.1% - 5%) of CNT can increase electrical and thermal conductivity. LM25 Al alloy has 91.5% Al, 6-7% Si, 0.25% Fe, 0.05% Mn, 0.2% Cu 1-1.2% Mg, 0.1% Ti in its combination providing low density, high castability, and low coefficient to thermal resistance and improved corrosion resistance. Frequent works had been performed in the area of CNTs and composites to aid the impertinent needs from the automotive and aerospace industries. CNTs; being the strongest and stiffest material yet discovered; are used in combat jets, bridge reinforcements, concrete reinforcements. Their conductivity and electromagnetic properties enable their usage in nanowires, conductive films, electric motor brushes, optical recognition etc. Basic ideas of Nano-technology and their significant applications in modifying material properties used in the large scale applications was given by Micro and Nanotechnology enterprise works.

The major properties of carbon nanotubes are that, they are the strongest and stiffest materials yet discovered in terms of tensile strength and elastic modulus. Electrical‐Carbon nanotubes caninfluence strongly electrical properties. Multiwall carbon nanotubes with interconnected inner shells show also super conductivity. The thermal conductivity and chemical kinetics are the other plus properties of the composite. One dimensional transport‐ carbon nano tube are frequently referred as one dimensional element because of the nano-scale dimensions electrons propagatesonly in tube’s axis direction. 

Amal etal [1] studied on conventional powder metallurgical techniques to reinforce the metal matrices. A powder rolling technique was used to fabricate CNT-reinforced aluminium strips. The Al-CNT mixture was blended in a mixer-shaker at 46 rpm prior to rolling process. The strength of the formed strips was evaluated for different wt% CNT samples and author stated 0.5% wt composite strips exhibited enhanced mechanical properties thanAluminium.

Biing-Hwa Yan et al. [2] studied on finishing process effects in the process of spiral polishing process. In micro-lapping process, dine in silicon and other micro-manufacturing process, the required surface finish need to be met and these surfaces were observed and studied in this work.

Del stark et al of Brussels [3] in 2006 investigated on the development of nano composite materials formed by different methods. Conducting organic polymers and CNTs were focussed on their study; considering recent development purpose.

HülyaCebeci et al. [4] studied on multifunctional properties of carbon nanotubes and carbon nanotube polymer composites. The composite were studied to enumerate the major properties getting enhanced on using CNTs as additives.

Enrique J. Lavernia et al. [5] investigated on mechanical properties of nanostructured materials, defined as having a mean grain size that falls in the 50-200 nm ranges, is reviewed and the underlying mechanisms are discussed. Particular emphasis is placed on nanostructured materials that are processed via two synthesis approaches consolidation of Nano-crystalline powders and electrode position. The review demonstrates that processing history significantly influence mechanical behaviours as revealed by the following observations.

Russelmcenzi [6] book on applied composite materials introduced the various property variations possible in composites especially when there is an application oriented approach done in developing the composite.

Amal M.K et al [7] investigated on potential and current challenges carbon nanotube reinforced composites. Observation regarding of remarkable mechanical properties exhibited by carbonnanotubes has stimulated much interest in their use to reinforce advanced composites.

Materials and Experimentation

Aluminium carbon nanotubes were prepared using a series of processes. Metal matrix was produced by using sand casting. Sand casting is one of the most popular and simplest types of casting. Sand casting allows for smaller batches to be made compared to permanent Mould casting and at a very reasonable cost. Three aluminium rods of diameters 20 mm and 380 mm length dimensions. These aluminium rods were machined on lathe. For making composite material an aluminiumalloy(LM25) as amatrix material because it is light metal and can be used for many purposes like making automobile parts, Airplane bodies etc.The composition of LM25 are
Fe‐0.259%,Si‐6.812%,Mn‐0.049%,Cu‐0.186%,Ni‐0.019%,Ti‐0.093%,Sn‐ 0.006%, V‐0.006%, Zn‐0.090%, Pb‐0.030%, Mg‐0.769%, Al‐91.676%. In carbon nanotube, a multi-wall carbon as it is comparatively cheaper than single wall carbon nano tube. Three samples are made one without carbon nanotubes, the other two with 3gm and 7gm of carbon nanotubes. The cast samples were then tested for hardness, tensile test and Izod test wear test & microstructure test. The hardness test is carried out by Rockwell hardness test and the results are projected.Similarly tensile test, Izod test, wear test&microstructure test of the three samples are also found out. The tested samples were then machined. The machining process was turning process in a lathe.Sand casting required a lead time of days for production at high output rates (1–20pieces/hr.-Mould) and was unsurpassed for large-part production. Green (moist)sand had almost no part weight limit, whereas dry sand had a practical
part mass limit of 2,300–2,700kg. Minimum part weight ranges from 0.075–0.1 kg. The sand was bonded together using clays, chemical binders, or polymerized oils. The mould consisted of silica, clay and water. When the water was added it developed the bonding characteristics of the clay, binding the sand grains together. When applying pressure to the mould material it can be compacted around a pattern, which was either made of metal or wood, to produce a mould having sufficient rigidity to enable metal to be poured into it to produce a casting. Process also uses coring to create cavities inside the casting.

Testing and results of Aluminium with MWCNT

The substitute material suggested here is to be used as a structural member in aircraft and marine
applications. Hence different properties need to be investigated before a valid suggestion. The
machined Aluminium bars were then subjected to tests such as hardness, tensile test, impact test,
and wear test and microstructure test analysis. The results were compared with each other.
Impact test is studied in the following table:-

 

Specimen size used was 75*10*10 having a notch depth of 2 mm. From this comparison optimum and minimum values of nano composites impact strength are clarified and then results are graphically plotted.

Hardness testing was done for the newly formed material and the results were compared with that of the aluminium monolithic alloy. The results were tabulated as shown below.

From the result 3gms of MWCNT mixed aluminium gave more hardnesscomparatively pure aluminium and 7gms of MWCNT mixed aluminium. Optimumand minimum hardness were plotted in graphs.

Tensile testing was performed on the aluminium specimen as well as the MWCNT added specimen
by following ASTM standard aspect ratio. The gauge length and diameter for the machine used was
270 mm and 11 mm diameters.

From the result report nano composites had more strength than aluminium alloy. In that mixture of 3gram and 7gram multiwall carbon nano tubes gave optimum and minimum strength. Results showed that 3gram of multiwall carbon nano tube gave more strength than 6gram of multiwall carbon nano tubes. From the result, calculation of the minimum and maximum points of strength could be easy.

The material was subjected to wear and friction test. The specimen size for performing the process was taken as length equalling 100 mm, and diameter as 8 mm. From the result nano composites had less wear resistance in both, with and without load conditions. Also the optimum and minimum wear resistance values are obtained in 3gm and 7gm multiwall carbon nano tubes mixture in aluminium LM25. The same results were obtained when the specimen with and without coating was subjected to friction testing at loaded and no loaded condition.

Conclusion

From the five different type of testing the nano composites gave better tensile strength, wear resistance, friction, hardness and impact strength, micro structure than the aluminium alloy. Usage of nano composites instead of aluminium alloy in the engineering field like automobile, aerospace and marine field where mechanical properties need to be more precise then what we get in alloys for preventing wear and friction like in the automobile cylinder. Regarding these applications, field cost could not cause a big problem, which resulted as the demerit of using nano composites. So to our conclusion nano composites can be handy and useful in such fields.

Posted by: Somu. in Science | Date: 18/12/2015

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