Experimental analysis of the thermal properties of fused quartz-reinforced Al-6061alloy matrix composites using RSM approach

Journal of Mechanical Science and Technology - This study investigates the thermal property of fused quartz-reinforced aluminum 6061 alloy metal matrix composites for three different chill material...     

Development of advanced fiber-reinforced polymer composites by polymer hybridization technique: Emphasis on cure kinetics,mechanical, and thermomechanical performance

Polymer hybridization technique, consisting of an interlayer arrangement of different polymers, acts as the most economical and promising technique in augmenting the glass fiber-reinforced polymer composite's mechanical properties. This investigation focuses on the effect of cure kinetics on the flexural behavior of glass-polymer hybrid (GPH) composite, and also elucidates the comparative analysis on the mechanical behavior of glass-epoxy (GE) composite, glass-vinyl ester (GVE) composite, and GPH composite. The optimal postcuring temperature has been found to be 200°C for GPH composite among the other postcuring temperatures conducted at 140, 170, and 230°C. Among all these abovementioned composites, highest flexural strength and interlaminar shear strength properties have been recorded by the 200°C postcured GPH composite leading to 10.87 and 18.76% increment, respectively, compared with GE composite. Furthermore, thermomechanical characterization has been done to know the viscoelastic behavior of the GPH composite postcured at different temperatures using dynamic mechanical thermal analysis. The fracture morphology of flexural tested composite samples demonstrated a combination of failure modes. Relevant information on the chemical restructuring and fracture morphology of experimented composite material using Fourier-transform infrared (FTIR) spectroscopy and Scanning electron microscopy (SEM) has also been studied.     

Effect of particle morphology on viscoelastic and flexural properties of epoxy–alumina polymer nanocomposites

Nanocomposites were synthesised by dispersing two different types of alumina nanoparticles in epoxy matrix by ultrasonication. Alumina nanoparticles of two shapes, rod and spherical were selected to investigate the effect of particle morphology on viscoelastic and flexural properties of nanocomposites. Specific surface area of both the selected nanoparticles was kept in the similar range. Good dispersion of nanoparticles was observed through transmission electron microscopy. The addition of nanoparticles in epoxy had significant enhancement in the viscoelastic properties and moderate improvement in flexural properties of composites. Composites having alumina nanorods showed higher improvement both in storage modulus as well as in flexural properties in comparison to composites having spherical alumina nanoparticles. Efficacy of Mori-Tanaka method was explored in modelling storage modulus of nanocomposites. Assorted size of alumina nanorods based on particle size distribution was used to model composites with nanorods to see the effect of size assortment on storage modulus.     

Antimicrobial efficacies of essential oils/nanoparticles incorporated polylactide films against L. monocytogenes and S. typhimurium on contaminated cheese

Polylactide based films were formulated by incorporating polyethylene glycol, selected nanopowders (zinc oxide, silver-copper), and essential oils (cinnamon, garlic, and clove) by solvent casting method. Films were tested against three foodborne pathogens (one gram-positive and two gram-negative) for their antibacterial activity. The effectiveness of selected cinnamon oil-based film was ascertained by performing a challenge test with cheese as a food model. In vitro antibacterial efficacies of nanopowders and essential oils were also determined by the decimal reduction concentrations and the minimum bactericidal concentrations for those foodborne pathogens. It was observed that nanopowders exhibited considerably poorer decimal reduction concentrations and minimum bactericidal concentration values in comparison to the essential oils. Silver-copper alloy nanopowders exhibited lower decimal reduction concentrations and minimum bactericidal concentrations values than ZnO against tested pathogens whereas essential oils showed distinct antimicrobial effectiveness against all those pathogens with in vitro decimal reduction concentration values of 87–157 and 77–220 µg/mL for cinnamon and clove oils, respectively. Among the various formulations, it was observed that only essential oils (especially cinnamon and clove) incorporated films exhibited a significant antimicrobial activity against the selected microorganisms. These results indicate that the poor antibacterial activity of the nanopowders and the hydrophobicity of polylactide could be responsible for the ineffectiveness of nanopowders in polylactide based films. Furthermore, the challenge test indicated the polylactide/polyethylene glycol/cinnamon oil film was appropriate to inhibit the growth of L. monocytogenes and S. typhimurium on cheese up to 11 days at refrigerated storage.     

Modeling of Tuning of Microresonator Filters by Perturbational Evaluation of Cavity Mode Phase Shifts

Microresonator filters, which are realized by evanescent coupling of circular cavities with two parallel bus waveguides, are promising candidates for applications in dense wavelength-division multiplexing. Tunability of these filters is an essential feature for their successful deployment. In this paper, we present a framework for modeling of tuning of the microresonators by changes in their cavity core refractive index. Using a reciprocity theorem, a perturbational expression for changes in the cavity propagation constants due to slight modifications of the cavity core refractive index is derived. This expression permits us to analytically calculate shifts in the spectral response of the 2-D resonators. Comparisons of the resultant shifts and spectra with direct simulations based on a coupled mode theory show satisfactory agreement.     

Fine grinding of thermoplastics by high speed friction grinding assisted by guar gum

High speed friction grinding has been used to grind plant and food substances in water but never been explored for grinding of thermoplastics like polylactic acid (PLA), low and high density polyethylene and polypropylene. Such grinding was investigated in this work and was made possible by using 0.5% guar gum solution instead of just water because increasing the viscosity of water reduced their settling and the speed of passing through the grinder. Tensile, flexural, and impact strengths of the plastics were studied and higher grinding efficiency of PLA could be explained by its low elongation-at-break compared to low density polyethylene, high density polyethylene, and polypropylene. The microplastics (2000–45 μm) were studied for mass and particle size distributions and by scanning electron microscopy, ¹³C CP/MAS NMR, Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. In addition, viscosity of guar gum and contact angles was measured. This new technology can produce finely ground microplastics (710–45 μm) for a variety of applications.     

Biocompatible tumor micro-environment responsive CS-g-PNIPAAm co-polymeric nanoparticles for targeted Oxaliplatin delivery

The objective of the research study was to develop and characterize a biodegradable, thermo and pH dual responsive Oxaliplatin-loaded chitosan-graft-poly-N-isopropylacrylamide (CS-g-PNIPAAm) co-polymeric nanoparticles as a tumor-targeting drug delivery system. CS-g-PNIPAAm co-polymers were synthesized, characterized and optimized its thermo and pH responsive properties for tumor microenvironment conditions. Optimized co-polymer could be efficiently loaded with Oxaliplatin in nanoparticle form, evaluated for their morphology (TEM), particle size, zeta potential, loading efficiency and drug content. In vitro drug release study at tumor microenvironment and physiological pH and temperature conditions. The in vitro drug release was optimal at above lower critical solution temperature (LCST) and tumor microenvironment pH when compared to physiological pH & temperature. MTT assay and fluorescence microscopic study showed that drug release and cell uptake was significantly enhanced in tumor microenvironment. In conclusion, the obtained nanoparticles appeared to be of great promise in tumor targeted drug delivery of oxaliplatin.     

Hydrodynamic lubrication of rough slider bearings with couple stress fluids

The combined effects of couple stresses and surface roughness on the performance characteristics of hydrodynamic lubrication of slider bearings with various film shapes, such as plane slider, exponential, secant and hyperbolic, are studied. A stochastic random variable with non-zero mean, variance and skewness is used to mathematically model the surface roughness of the slider bearing’s. The Stokes couple stress fluid model is used to characterize the rheological behavior of the lubricant with polymer additives. The modified expressions for the bearing characteristics, namely pressure, load carrying capacity, center of pressure, frictional force are obtained for the general lubrication film shape on the basis of Stokes microcontinuum theory for couple stress fluids. Results are computed numerically for various film shapes under consideration. It is observed that, for all the lubricant film shapes under consideration, the negatively skewed surface roughness increases the load carrying capacity, frictional force and temperature rise, while it reduces the coefficient of friction. On the contrary, the reverse trend is observed for positively skewed surface roughness. Further, these effects are more pronounced for the couple stress fluids.     

Effect of surface roughness on the couple-stress squeeze film between a sphere and a flat plate

In this paper, a theoretical study of the effect of surface roughness on the hydrodynamic lubrication of couple-stress squeeze film between a sphere and a flat plate is presented on the basis of Christensen's stochastic theory for hydrodynamic lubrication of rough surfaces. The modified Reynolds equation accounting for the couple stresses and the surface roughness is mathematically derived. The modified Reynolds equation is solved for the fluid film pressure and the bearing characteristics, such as the load carrying capacity and the time–height relationship, are obtained. It is found that the surface roughness considerably influences the squeeze film characteristics. The load carrying capacity and squeeze film time are found to increase for an azimuthal roughness pattern as compared to the corresponding smooth case, whereas the reverse trend is observed for a radial roughness pattern.