Epoxy resins are prone to serious moisture absorption inspite of their inherent advantages, which can be mitigated by the incorporation of montmorillonite nanoclay that provide tortuous path to flow of moisture. Moisture absorption studies of epoxy clay nanocomposites is carried out, to analyse the effect of nanoclay content, immersion media and immersion temperature. Nanocomposites prepared in 0.5, 1 and 1.5 wt% using magnetic stirring and ultrasonication and neat epoxy specimen were immersed in distilled water and artificial seawater maintained at 28 and 38 °C till saturation. Fick’s and Langmuir’s models were applied to calculate the kinetic parameters from the water absorption graphs. Atomic force microscopy (AFM), X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope with energy dispersive X-ray (SEM–EDX) characterizations were performed. Diffusivity is least for nanocomposite containing 0.5 wt% nanoclay at both temperatures in both medium. However, it is least when the medium is distilled water. As the temperature of immersion medium increases, the diffusivity also increases. Saturation moisture uptake increased with increase in nanoclay content, because of the residual hydrophilic nature of nanoclay. AFM and XRD analysis revealed better dispersion and exfoliated structure of nanoclay respectively at 0.5 wt% loading. FTIR spectroscopy was applied to identify the chemical bonds that helped in proposing the reaction mechanism of the nanocomposite synthesis. Spectra comparison of dry and wet specimens complimented the moisture absorption data by showing lower infrared transmittance in wet specimens. With Increase in nanoclay content, the transmittance decreased corresponding to increase in saturation moisture uptake for distilled water immersed specimens. SEM–EDX analysis distinguished between the cations entered from the artificial seawater and cations that were still present in the nanoclay.
The purpose of this research is to investigate the effect of heat treatment parameters on the tool life and surface roughness of dual phase steel. Optimization of machining parameters (cutting speed, feed and depth of cut) is carried out for the machinability tests on medium carbon low alloy steel. Taguchi's method of design is used to carry out machinability tests. Analysis of variance (ANOVA) is carried out to determine the relative contribution of machining parameters on tool life and surface roughness. Microstructure analysis is carried out to ascertain the machining behavior of the steel. Results have shown that, depth of cut and cutting speed are the most significant factors contributing on the variation of the tool life and surface roughness. Optimized machining parameters are calculated in order to obtain higher tool life and lower surface roughness value.
Aluminium alloy based metal matrix composites are being extensively used in the aerospace, automobile, defense, marine and electronic industries owing to their excellent strength, high resistance to wear, corrosion and better thermal stability. Many investigators have explored different aluminium alloy series composites, like heat treatable AA2024, AA6061 and AA7075 since the properties of these matrix alloys can be easily tailor made to suite specific application due to easy processability and heat treatability. AA7075 alloy matrix is predominantly being used, as it exhibits high ultimate tensile strength, resistance to corrosion and fatigue in the group. In the current review work, attention is focused to present types of reinforcing materials used, benefits of reinforcement hybridization, methods employed for composite production and critical property analysis, with conclusions of experimentation and the suggested prospective applications of AA7075 composites. Due to good castability and moldability variety of processing techniques in solid, semisolid and liquid states are possible. As matrix alloy, low processing temperature, ability to accommodate reinforcements and adoptability to different reinforcing techniques, it is easy to obtain optimal properties as per the application. AA7075 with small addition of copper is paved the path in the field of electronic and military applications due to high thermal and electrical conductance. Even pure metal addition & magnesium with copper facilitate good weldability, plasticity and corrosion resistance. Due to the flexibility in accommodating carbide and oxide compound reinforcements in the matrix, this matrix composite widens versatility limit due to excellent hardness and wear resistance. CNT and graphite reinforcements to this aluminium series matrix are marked as ultra-high precision components in defense field.
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