Applied Mechanics and Materials Vol. 787

Abstract: Silicon carbides is a composite ceramic material produced from inorganic non-metallic substances, formed from the molten mass which solidifies on cooling and simultaneously matured by the action of heat. It is used in various applications such as grinding wheels, filtration of gases and water, absorption, catalyst supports, concentrated solar powers, thermoelectric conversion etc. The modern usage of silicon carbide is fabricated as a heat exchanger for high temperature applications. Leaving behind steel and aluminium, silicon carbide has an excellent temperature withstanding capability of 1425°C. It is resistant to corrosion and chemical erosion. Modern fusion reactors, Stirling cycle based gas turbines, evaporators in evaporative cooling system for air condition and generator in LiBr/H₂O absorption chillers for air conditioning those systems heat transfer rate can be improved by replacing a present heat exchanger with silicon carbide heat exchanger. This review presents a detailed discussion about processing technique of such a silicon carbide. Modern known processing techniques are partial sintering, direct foaming, replica, sacrificial template and bonding techniques. The full potential of these materials can be achieved when properties are directed over specified application. While eyeing over full potential it is highly dependent on processing techniques.

Abstract: The Fibre Reinforced Plastic (FRP) composites are extensively used for a wide variety of applications in automobile, aerospace, chemical, biomedical and civil engineering fields due to their excellent properties. Composite materials offer significant advantages in strength-to-weight ratio and corrosion resistance over metallic materials. Initially FRP composites were based mainly on thermoset polymers because of the ease of manufacturing. But, recently FRP composites using thermoplastics matrices are gaining importance because of their advantages over thermoset composites. In the present work, FRP laminates were fabricated using glass fabric and carbon fabric as reinforcements and thermoplastic polymer (polypropylene) as matrix. Fiber Reinforced Thermoplastics (FRTP) laminates of glass fibre /polypropylene (GF/PP), carbon fibre/ polypropylene (CF/PP) and glass-carbon fibre /polypropylene (GF/CF/PP) hybrid composite laminates were fabricated by film stacking method using hot compression molding press under optimum process parameters (pressure, temperature and dwell time). The fabricated FRTP laminates were tested for various mechanical and physical properties viz., tensile strength/modulus, flexural strength/modulus, izod impact strength, moisture absorption, barcol hardness and density as per relevant ASTM standards. The results of the tests carried out on three materials were compared. It was observed that hybrid laminate (GF/CF/PP) is superior in flexural strength/modulus as compared to GF/PP but the little lower mechanical properties compared to CF/PP laminates. But use of hybrid laminates has great cost advantage compared to CF/PP.

Abstract: Aluminium reinforced with SiC, Al₂O₃ and B₄C etc. possesses an attractive combination of properties such as high wear resistance, high strength to weight ratio and high specific stiffness. Among the various reinforced materials used for aluminium, B₄C has outperformed all others in terms of hardening effect. Particle size reduction of B₄C is found to have positive impact on the material hardness. In the view of physical properties, B₄C has less density than that of SiC and Al₂O₃, which makes it an attractive reinforcement for aluminium and its alloys for light weight applications. In this work, Al nano B₄C composite prepared by ultrasonic cavitation method was machined by Abrasive assisted electrochemical machining using cylindrical copper tool electrodes with SiC abrasive medium. In this paper, attempts have been made to model and optimize process parameters in Abrasive assisted Electro-Chemical Machining of Aluminium-Boron carbide nano composite. Optimization of process parameters is based on the statistical techniques using Response Surface Methodology with four independent input parameters such as voltage, current, abrasive concentration and feed rate were used to assess the process performance in terms of material removal rate and surface finish. The obtained results were compared with abrasive assisted electro chemical machining of Aluminium-Boron carbide micro composite and the effect of particle size on the process parameters was analyzed.

Abstract: Artificial hip joints have been implanted throughout the world into patients suffering from disabling hip joint disease, to restore their painless joint function. This means replacing the femoral head and acetabular socket with artificial prosthetic components. In order to obtain artificial implants with enhanced physical, chemical, mechanical, biological and tribological properties resulting in the accelerated self-adaptation of human body and long term performance, it is necessary to combine the advantages of materials with various properties; biocompatibility, bioactivity, excellent corrosion resistance, high fatigue and tensile strength, low modulus of elasticity, coefficient of friction, and high wear resistance. The present work focuses on investigating the wear rate of multi-layer coatings for different combinations in order to reduce the wear rate of the prosthesis. Three different combinations of multilayer coating were deposited by plasma arc spraying technique on titanium. It was found that the multi-layer coating consists of Alumina as a primary coating and Zirconia as the secondary coating provides lower wear rate and higher hardness compared to other combinations which would give optimal performance and thereby increasing its longevity.

Abstract: In this investigation, conventional hand layup method was employed to fabricate hybrid epoxy laminate composite. Jute fiber, E-glass fiber and carbon fiber fabrics of 500,200,200 gsm respectively were used as a reinforcements and epoxy with k-6 hardener was used as a matrix material. Tensile, compression and flexural tests were conducted as per the ASTM standards. It is observed that jute/carbon/epoxy laminate of 2mm thickness plate exhibits significant mechanical properties compare to jute/glass/epoxy laminate of 2mm laminate composite.

Abstract: With the frequent change in technology and the need of materials with improved mechanical properties like tensile strength and hardness without any substantial increase in density, research in the area of metal matrix plays a key role in fulfillment of such requirements. The Aluminum 64430 is used for manufacturing general engineering items like vehicles, rail, bridges, cranes and other automotive parts. The aim of this study is to synthesize and characterize alloy Al 64430 by reinforcing it with SiC wt% of (0%, 3% and 6%) through liquid metallurgy route in order to achieve improved tensile strength and hardness in comparison to base Al alloy 64430. The optical micrographs disclose the consistent distribution of SiC particles in matrix. The mechanical tests of the composite resulted in increased tensile strength and hardness with the increase in SiC wt% in comparison to base alloy Al 64430.

Abstract: The flexural modulus of composite laminates subjected to cyclic loads of varying cycle periods are experimentally investigated in this work. GFRP composite laminate specimen of configuration 0/R/0/0/0, 0/R/30/60/0, 0/R/90/90/0 and 0/R/45/-45/0 are prepared by hand lay-up technique with a uniquely processed resin-rich intermediate layer for the testing. Specimens are exposed to constant amplitude cyclic loading of frequencies 4.6 Hz and 8.6 Hz. A cantilever configuration of specimen with cyclic tip loading is considered to simulate the conditions of a leaf of a laminated automobile leaf spring. The flexural response of the laminate is measured using three point bend test as per ASTM D 790 and damping by hysteresis loop. The observed reduction in flexural modulusand the increase in damping factor after loading are compared with virgin. Minimised flexural modulus deviations between the loading frequencies are favoured by the cushioning of resin rich intermediate layer in the lay-up.

Abstract: Increasing concern about the environmental pollution, clear understanding of uncertainty of petroleum products resulted in the utilization of eco-friendly materials. In the present work dora hemp natural fibre is made into particulate form through chemical treatment. Then it is reinforced at 3.98 wt % into the polyester matrix to fabricate the composite lamina by “Two Stage Wet Layup”. A special focus is made in describing the hand/wet lay-up procedure. The post cured and machined composite specimens as per ASTM procedures are tested to determine the mechanical properties. Dora hemp particulate composites have showed the tensile strength, modulus 12.57 MPa, 197.47 MPa respectively. In the bending load they have showed a flexural strength, modulus of 38.08 MPa, 1.78 GPa respectively. The composites under the impact load had shown impact strength of 1.38 kJ/m².

Abstract: Metal matrix composites (MMCs) play a vital role in today’s engineering industries. Stir casting is one of the most inexpensive methods for the production of particulate reinforced metal matrix composites. However there are few problems encountered in stir casting such as the problem of poor wettability of the reinforcement particles in the matrix metal. The reinforcement particles have the tendency to either settle at the bottom of the crucible or they tend to float at the top of molten metal. This is due to the greater surface tension of the molten metal. Various techniques are available to improve the wettability of the ceramic particles in metal matrix which includes Particle treatment, Particle coating and Addition of alloying agent. In this work, Magnesium (Mg) was used as the alloying element to improve the wettability of SiC particles in the Al matrix. Mg is used to reduce the surface tension of molten aluminum (Al) thus promoting proper wetting. To understand the effect of Mg on improving the wettability of SiC in aluminum matrix, different weight percentages of SiC particles reinforced aluminum alloy 6061(AA6061) based MMCs were fabricated in stir casting method by adding Mg as alloying element. The cast specimens were subjected to microstructural analysis, tension tests and hardness tests. Results showed that addition of Mg with SiC in AA6061 matrix significantly improved the wetting between Al and SiC; subsequently MMCs possessed enhanced mechanical properties.

Abstract: In this work, AA6061/1.25 vol. % SiC_p metal matrix nanocomposites (MMNCs) were fabricated using the ultrasonic cavitation assisted casting process. To investigate the effect of ultrasonic amplitudes on processing the MMNCs, the MMNC samples were processed with 15 µm, 30 µm and 50 µm of ultrasonic amplitudes. The results indicate that the ultrasonic amplitudes play a significant role in dispersing the SiC nanoparticles uniformly in the AA6061 melt and it also affecting the mechanical properties of the fabricated MMNCs. The AA6061/1.25 vol. % SiC_p MMNC sample processed with 30 µm of ultrasonic amplitude possessed the good dispersion of SiC_p in the Al melt and hence better mechanical properties compared to the MMNCs processed with 15 µm and 50 µm amplitudes.