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Carbon fibre-reinforced polymer composites are finding increased applications in the field of automotive manufacture and aircraft industries due to their appreciative combination of high strength and low weight. The machining of these composites with economically viable and high part qualities requires enhancement in machining strategies. Delamination and surface roughness are the undesirable geometrical defects inherent in abrasive jet machining of layered polymer composites. This investigation focuses on the mechanism of delamination and surface roughness in abrasive jet machining of carbon fibre-reinforced polymer composite. The paper endeavors at the exploration of the viability of imparting swirling motion to SiC abrasive particles by presenting internal threads in the newly designed nozzle. In this research, a novel threaded nozzle was introduced in the abrasive jet machine for making holes on the carbon fiber-reinforced polymer composites with the objective of reducing the delamination and surface roughness. This is a distinctive attempt of its kind and this has brought down the delamination factor considerably and, as a consequence, surface roughness obtained was minimum. Holes were made on carbon fiber-reinforced polymer composite by abrasive jet machining with a modified nozzle with and without an internal thread. The influence of abrasive jet parameters on the delamination factor (bottom and top) and surface roughness (Ra) was investigated. Maximum pressure and minimum SOD cause decrease in delamination and surface roughness in carbon fiber-reinforced polymer composite composites. [ABSTRACT FROM AUTHOR]

This paper attempts at investigation of the feasibility of imparting a swirling motion to abrasive particles by introducing internal threads in the nozzle. In this investigation, a novel internal threaded nozzle was introduced in the abrasive jet machine to make holes on the carbon fiber reinforced polymer composites with the objective of reducing the machining time. This is a unique attempt of its kind and this innovation has brought down the machining time considerably and, as a consequence, higher material removal rate was obtained. Carbon fiber reinforced polymer composites are inhomogeneous and coarse in nature, and hence, the ease of machining and the machining time are always challenging. A morphological study was also made using an optical microscope to find the kerf width and kerf angles. The effect of two different nozzles on machining time, material removal rate, and kerf analysis on the carbon fiber reinforced polymer composite was investigated. It was found that machining time was reduced by 92% with novel internal threaded nozzle. The nozzle with internal threads also reduced the kerf angle of the machined hole. [ABSTRACT FROM AUTHOR]

Abstract: The SiCf/SiC ceramic matrix composites find applications in structural, wear resistance and high temperature applications as they are quite superior to their monolithic counter parts due to their improved flaw tolerance, large work of fracture and non-catastrophic failure behaviour. In this investigation, three types of SiCf/SiC composites, i.e., SiCf/SiC composite with carbon interface, SiCf/SiC composite with boron nitride interface and SiCf/SiC composite with boron nitride interface subjected to an intermediate heat treatment have been made via isothermal and isobaric chemical vapour infiltration technique using Nicalon ceramic grade SiC fibres. The density achieved in all the three types of composites is around 2.6–2.7g/cc. The sliding wear/friction and solid particle erosion experiments were carried out on these composites using a pin-on-disc set up and jet erosion test rig respectively. The composites with carbon interface show higher hardness, lower sliding wear and erosion losses compared to the composite with boron nitride interface with and without intermediate heat treatment. To substantiate the slide wear and erosion data, scanning electron microscopic features have been examined. [Copyright &y& Elsevier]

The composites are classified as metal matrix composites, polymer matrix composites, and ceramic matrix composites. Many different matrices have been tried over the years in the MMC formulations but aluminum has been most exploited for compositing due to its low density and ease of fabrication. These composites have received considerable attention as a potential advanced material for application in automobile, aerospace, defense, and general engineering sectors. In this investigation, an attempt has been made to fabricate Al-SiCp composite material by powder metallurgy technique at different volume percentage of reinforcements (5, 10, 15, 20, and 25%). The corrosion behavior of the composite was analyzed using AC Gill potentiostat with 3.5wt% NaCl medium. Four factors, five levels, and a central composite rotatable design matrix is used to minimize the required number of experiments. The effect of metallurgical factors on the corrosion behavior of the composite was analyzed. The factors include volume percentage of reinforcement, particle size, pH, and reverse potential. [ABSTRACT FROM AUTHOR]

Abstract: Aluminium alloy matrix composites with carbon fibre reinforcement were prepared by stir casting method. In order to avoid any interfacial reactions in the carbon fibre reinforced composites, the carbon fibres were coated with copper. The fibres were coated by electroless coating method and then characterized. Composites containing different amounts of carbon fibres were prepared by stir casting and then subjected to age-hardening treatment. Fibre distribution was fairly uniform in the composites containing up to 4wt% carbon fibres. Tensile strength of the composites was found to be increasing up to 4wt% carbon fibre. [Copyright &y& Elsevier]

In this investigation an attempt has been made to fabricate Al-SiCp and Al-Al2O3 composite materials by powder metallurgy technique at different volume percentage of reinforcement (5, 10, 15, 20, and 25%). The corrosion behavior of the composites were analyzed using AC Gill potentiostat with 3.5 wt% NaCl medium. Four factor, five level, central composite, rotatable design matrix is used to optimize the required number of experiments. The mathematical models were developed by the response surface method (RSM). The developed models have been checked for their adequacy and significance by the F-test and t-test, respectively. The results obtained from the mathematical models have been optimized and also tested using conformity test runs. [ABSTRACT FROM AUTHOR]

Nanocomposite gel coat system is prepared using unsaturated polyester resin with aerosil powder, CaCO3, and organoclay. The influence of organoclay addition on mechanical and water barrier properties of gel coat system is studied for different amount (1,2, and 3 wt %) of organoclay. The nanolevel incorporation of organoclay improves the mechanical and water barrier properties of nanocomposite gel coat system. The nanocomposite gel coat system exhibits 55% improvement in tensile modulus and 25% improvement in flexural modulus. There is a 30%improvement in impact property of nanocomposite gel coat system. The dynamic mechanical analysis shows a slight increase in glass transition temperature for nanocomposite gel coat system. [ABSTRACT FROM AUTHOR]

Presents a letter to the editor about the flexural and tribological properties of polyester-clay nanocomposites.

Reaction bonded silicon nitride (RBSN) composites containing 10 vol% carbon fiber were prepared using the direct nitridation method at 1200, 1300 or 1400 °C by purging pure nitrogen or nitrogen-hydrogen (95% N 2 -5% H 2 ) mixed gas. The effect of nitridation temperature and gaseous medium on the microstructure of RBSN were studied in detail. X-ray diffraction analysis on the resultant RBSN composites revealed a dominant α-Si 3 N 4 phase along with β-Si 3 N 4 and Si 2 N 2 O. The growth of silicon nitride whiskers was found to increase with the addition of carbon fibers. The microstructural analysis using TEM and SEM ascertained that there was no formation of beads at the tip of the whiskers. Hence, the growth of whiskers purely depends on gas phase reactions, i.e., it is based on vapor-solid (VS) and not vapor-liquid-solid (VLS) mechanism. [ABSTRACT FROM AUTHOR]

Abstract: Synthesis of 2D SiCf /SiC composites for applications in fusion reactors is a challenging task due to the stringent specification requirements on various mechanical and thermo-mechanical properties, chemical compatibility (with Pb–Li), oxidation resistance and irradiation resistance. Three types of SiCf/SiC composites with C interface and BN interface, with and without intermediate heat treatment are prepared through isothermal and isobaric chemical vapor infiltration process. Dense SiC seal coat applied to the composites has improved their oxidation resistance. The tensile, flexural and fracture toughness values of composite with BN interface were found to be improved by stabilizing the BN interface through thermal treatment. The electrical and thermal conductivity values obtained for composites with C interface are in the range of 10–29S/m and 2.5–3.25W/mK for the temperature range 500–900°C as required for fusion reactor applications. [Copyright &y& Elsevier]

Abstract: Ceramic heat exchangers are increasingly used in many nuclear power plants. Silicon carbide has been treated as a promising material for heat exchanger application since it has good thermal conductivity and corrosion resistance. In this work, four different types of Si/SiC ceramic composites were prepared by liquid silicon infiltration technique. Thermal conductivities of these ceramic composites at different temperatures are measured by the laser flash thermal conductivity method. Results show that the presence of free carbon and voids are notably affecting the thermal conductivity of these materials. [ABSTRACT FROM AUTHOR]

Abstract Carbon fiber (C f) reinforced reaction bonded silicon nitride (RBSN) composites with various amounts of fiber (5, 10, 15 and 20 vol %) are fabricated at 1400 °C using the direct nitridation method. The effect of C f on the phase formation, microstructure evolution, mechanical and dielectric properties has been investigated. The XRD analysis using Rietveld refinement shows the presence of alpha and beta silicon nitride with a trace amount of tungsten disilicide. Microstructural analyses show the uniform dispersion of C f in the RBSN matrix and the different toughening mechanisms operated in the composites. Mercury intrusion porosimetry results show unimodal to the multimodal distribution of pores with the increase in the quantity of C f. The porosity of the composites varies from 30 to 38% with the addition of C f. The addition of C f has enhanced the fracture toughness of the composites only with 5 vol % C f and the maximum toughness achieved is 2.5 MPa m1/2. There is no interface reaction on the C f , which indicates the stability of fibers in the nitrogen atmosphere at 1400 °C. The dielectric performance of the composites in the X-band frequency range (8.2–12.4 GHz) is found to increase with C f content. Graphical abstract Image 1 Highlights • Short carbon fiber reinforced silicon nitride composites were fabricated by reaction bonding method. • The increase of carbon fiber content has increased the porosity of the composites. • Pore size was varied from monomodal to multimodal distribution with the addition of carbon fibers. • Carbon fiber addition has enhanced the mechanical and dielectric properties of the composites. [ABSTRACT FROM AUTHOR]

Abstract: Solid particle erosion tests were conducted on four different types of silicon carbide ceramic composites. The composites are cotton fabric based Si/SiC with and without chemical vapour infiltration, fine teak wood powder based Si/SiC and coarse teak wood powder based Si/SiC. The erodents used are angular SiC particles of average size 80, 250 and 450μm. The velocities with which particles impacted on the target materials were varied from 20 to 50m/s. Similarly the angle of impact was varied from 20° to 90°. Scanning electron microscopic observations on the eroded surface show brittle and cleavage like fracture. Fine teak wood powder based Si/SiC ceramic shows better erosion resistance than the other ceramics. Homogenous distribution of SiC grains with the presence of very fine grains of silicon and carbon is responsible for the improved erosion resistance. The higher erosion rate in cotton fabric based SiC arises from its microstructure. Here, the free carbon and free silicon grains are large in size and the SiC phase has very low hardness as compared to the erodent. [Copyright &y& Elsevier]

Abstract: SiCf/SiC composites are class of high temperature structural materials being developed for use in nuclear fusion and fission reactor systems because of their superior high temperature mechanical properties, low radiation damage and low induced radioactivity. Two types of 2D SiCf/SiC composites were made through isothermal and isobaric chemical vapor infiltration process using eight harness satin-woven ceramic-grades Nicalon™ fibers with boron nitride (BN) interface, namely: one with lower interface thickness and a second type with higher interface thickness. The BN interface was applied to the fiber prior to SiC matrix addition to modify the interfacial bond strength leading to better toughness and improved oxidation resistance. The density achieved was around 2.6g/cc. The composite specimens were subjected to thermal cycling treatment using an in-house furnace. The mechanical properties such as tensile strength, fracture toughness and interfacial bond strength were also studied for all the composites before and after thermal cycling. It is seen from the results that both composites withstood thermal shocks and thermal cycling treatment. It was also concluded from the present work that good balance between load transfer and crack arresting was established. [Copyright &y& Elsevier]