Investigation of hybrid ultrasonic machining process of Nomex honeycomb composite using a toothed disc cutter.

Nomex honeycomb composite (NHC) has been increasingly used in the automotive, aerospace and defence applications due to its excellent thermal and mechanical properties. Its complex cellular hexagonal thin-walled configuration along with heterogeneous, soft and brittle nature pose substantial processing defects such as burr formation, tearing of walls, surface roughness, dimensional inaccuracy and low machining quality during conventional machining (CM). These surface defects have a substantial influence on the operating life and functional performance of its sandwiched structural members. Hybrid ultrasonic vibration assisted machining (HUSVAM) technology has been introduced to overcome such limitations. For an in depth research on HUSVAM of NHC using ultrasonic toothed disc cutter (UTDC), three dimensional finite element model was developed and experimental validation was carried out. The numerical simulation and experimental results were found to be in good agreement with one another. The influence of various machining parameters including the ultrasonic tool vibration amplitude (UTVA), feed rate (FR), depth of cut (DoC) and spindle angular speed (SAS) on NHC cutting forces, chip formation and surface quality was investigated using both HUSVAM and CM techniques. Furthermore, stresses, deformation and forces near tool-workpiece interaction along with the surface topography and morphologies were also analysed and compared for various operating conditions. A reduction in the cutting forces was found with the increase of SAS and UTVA (up to 65.47 % and 65.74 %, respectively). Although, the cutting forces were observed to increase by increasing the DoC and FR (up to 159.45 % and 126.33 %, respectively). DoC has a greater impact on the cutting forces among all machining parameters according to 4 levels, 4 factors (L16) orthogonal experiments based on Taguchi method. The results show that the chip formation and machining quality of NHC core can be improved with HUSVAM technique using UTDC. HUSVAM also reduced the cutting forces (up to 73 %) compared to CM. The ultrasonic toothed disc cutter generated large number of burr with very short length, no tearing defects and no uncut fibers as observed from scanning electron microscopy of NHC hexagonal cell structure, walls and triple points. A burr formation of less than 10 % was realized during HUSVAM of NHC cores for Fx≤3N, while it was found up to 20 % if Fx>3N, compared to at least 40 % during CM. The finite element model developed can be used to investigate the influence of HUSVAM on modern difficult to machine materials for enhanced surface quality.

Novel polyaniline-polyethersulfone nanofiltration membranes: effect of in situ polymerization time on structure and desalination performance.

In this research, novel polyaniline-layered nanofiltration membranes were prepared by phase inversion of base polyethersulfone (PES) membranes and subsequent in situ solution-phase deposition of polyaniline as a thin surface layer. In these composite membranes, the impact of the polyaniline deposition time on steric hindrance and electrostatic interactions during permeation was elucidated. The chemical structure, thermal stability, and mechanical properties of the PES and PANI-PES membranes were investigated using Fourier-transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA), respectively. The membranes' porosity and pore size decreased as PANI deposition time increased. As PANI deposition time increased, PANI layered nanofiltration membranes exhibited improved thermal stability but deteriorated mechanical characteristics due to free radical destruction from prolonged exposure to the oxidant. These PANI-PES membranes showed 43% rejection (NaCl) at 1.7 bar coupled with a flux of 11.59 L h-1 m2 that is quite promising when comparing with similar Nanofilteration (NF) membranes in the literature and commercial NF membranes, as well. As the deposited layer, PANI is partially doped; hence, permeation results have been interpreted in terms of steric hindrance and electrostatic repulsion by electrochemical PANI layering.

Heterogeneous ion exchange membranes based on thermoplastic polyurethane (TPU): effect of PSS/DVB resin on morphology and electrodialysis.

In this research, novel heterogeneous cation exchange membranes based on thermoplastic polyurethane (TPU) have been prepared by the solution casting technique. The effects of incorporation level of sulfonated polystyrene divinyl-benzene (PSS/DVB) resin on water uptake, ion exchange capacity, membrane potential and salt extraction have been elucidated. Morphological and water uptake studies suggested a two-phase heterogeneous membrane morphology owing to the presence of hard and soft segments in the TPU backbone and swelling of PSS/DVB particles. This morphology was shifted to a semi-gelled morphology throughout the membrane bulk when resin loading exceeded 50 wt%. The physically cross-linked hard segments in the TPU backbone ensured a compact membrane morphology and prevented the formation of water channels. The membrane potential showed that increasing the resin content increased the membrane transport number (max. 0.95) up to 50 wt% resin loading and beyond this, the transport number started decreasing showing a pronounced effect of voids and water flow channels developing on excessive swelling. The permselectivity reached a maximum (up to 0.92) and salt extraction values also increased (by varying voltage) up to 50 wt% loading and started decreasing beyond this optimum content. This study shows successful development of low-cost heterogeneous cation exchange membranes based on TPU with acceptable electrochemical properties.

EFFECT OF POLYMER AND PLASTICIZER ON THIN POLYMERIC BUCCAL FILMS OF MELOXICAM DESIGNED BY USING CENTRAL COMPOSITE ROTATABLE DESIGN.

Aim of the present work was to design fast dissolving buccal film of meloxicam using central composite rotatable design and to evaluate the effects of polymer and plasticizer on formulation and characterization of the buccal films. Meloxicam was incorporated in film as model drug, HPMC E15 was used as film forming agent and polyethylene glycol (PEG) 400 was used as plasticizer. Films were fabricated using solvent casting technique. Prepared films were subjected to study various evaluation parameters. Dissolution studies were carried out for 30 min, using phosphate buffer of pH 6.8. Drug-excipients compatibility was studied using Fourier transform infra-red spectroscopy (FTIR). X-ray diffractometry (X-RD) was used to observe the crystalline or amorphous nature of the drug. Differential scanning calorimetry was used for thermal analysis of the drug and films. Optical microscopy and scanning electron microscopy were used to study the surface morphology. Results revealed that apparently the films were of smooth surface with uniform mixing of drug and excipients. Folding fortitude was > 100 in all the formulations. Weight variations were in acceptable range. Moisture loss was directly linked with concentration of plasticizer. Although buccal films were showing rapid release of the drug but still it was noticed that increasing concentration of HPMC E15 was the cause of drug retardation as well as delay in the total dissolution time, while PEG 400 was facilitating the drug release from the formulated films. Formulation F5 released approximately 100% drug in 5 min. All formulations individually showed total dissolving time in the range of 48-120 s. There were no noticeable interactions between drug and excipients. Finally, it was concluded that meloxicam containing films can be optimized using statistical tools, and HPMC E15 in combination with PEG 400 as plasticizer can be effectively used in the films formulation.

Synergistic Effect of Functionalized Nanokaolin Decorated MWCNTs on the Performance of Cellulose Acetate (CA) Membranes Spectacular.

In order to enhance salt rejection level and high pressure mechanical integrity, functionalized nanokaolin decorated multiwall carbon nanotubes (FNKM, 0-5 wt % loading) were incorporated into a cellulose acetate (CA) matrix using high temperature solution mixing methodology. Scanning electron microscopy (SEM), X-ray diffraction technique (XRD), thermo-gravimetric analyzer (TGA) and Fourier transform infrared spectrometer (FTIR) were used to characterize the prepared membranes. The obtained results revealed that with increasing FNKM concentration in the host polymeric matrix, composite membrane's structural, functional, thermal, water permeation/flux and salt rejection characteristics were also modified accordingly. Percent enhancement in salt rejection was increased around threefold by adding 5 wt % FNKM in CA.