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Corrosion inhibition of 2024-T3 aluminum alloy in 3.5% NaCl by thiosemicarbazone derivatives
No full textThree thiosemicarzone derivatives, namely (E)-2-(2-hydroxybenzylidene) hydrazinecarbothioamide(MHC), (E)-2-(2,4-dihydroxybenzylidene)hydrazinecarbothioamide (DHC) and (E)-2-(2,3,4-trihydroxybenzylidene)hydrazinecarbothioamide (THC) were synthesized and their corrosion inhibition action on 2024-T3 aluminum alloy was studied in 3.5% NaCl solution. The surface morphology and surface composition of the corroded alloy were examined using FESEM, 3D profilometry, EDX spectroscopy and X-ray photoelectron spectroscopy. The synthesized inhibitors were found to provide corrosion protection on AA2024-T3 by forming an adsorbed layer of the complex on the alloy surface. They exhibited inhibition efficiency in the order, MHC < DHC < THC. Quantum chemical calculations corroborated the experimental results
Numerical Study and Experimental Validation of Effect of Varying Fiber Crack Density on Stiffness Reduction in CFRP Composites
No full textRepresentative volume element (RVE) has commonly been used to predict the stiffness of undamaged composite materials using finite element analysis (FEA). However, never has been an independently measured true microstructural damage quantity used in FEA to predict composite stiffness. Hence, in this work, measured fiber crack density in unidirectional fiber composite (generated using controlled fatigue loading) was used to predict reduction in stiffness using a RVE. It was found that the stiffness changes with change in depth of the volume element along the fiber direction and asymptotically reaches a constant value beyond a critical length called representative depth. It was argued that this representative depth should be more than the minimum of two characteristic length scales, twice of ineffective length and average length of broken fibers. Effective stiffness obtained from FEA of the optimum-sized RVE was in excellent agreement with the experimental results for given microstructural damage state
Influence of soft segments on thermo-mechanical behaviour of novel epoxy based shape memory polymers.
Get PDFEpoxy based Shape Memory Polymers (SMEPs) have been formulated by reacting an aerospace grade aromatic epoxy resin with aliphatic amines. TETA (triethylenetetramine) series and TTD (trioxatridecanediamine) series SMEPs with varying soft segment contents and with glass transition temperatures (Tgs) ranging from 103-51°C have been obtained. The viscoelastic behaviour of SMEPs has been investigated using an Advanced Rheometric Expansion System (ARES). For the thermomechanical tests, the respective Tg of each SMEP has been fixed as the deformation as well as recovery temperature (shape switching temperature). Further, the effect of soft segments on thermo-mechanical shape memory behaviour of the SMEPs has been evaluated. The results reveal that TTD series SMEP with maximum soft-segment content exhibit a narrow viscoelastic region, complete shape recovery and very good shape memory behaviour. Thus based on specific applications the soft segment content may be varied suitably
Fabrication & Characterization of Hybrid fibers and Hybrid Fiber reinforced composites - A Novel Approach}.
No full textThe hybridfibers were made by coating MWNT on the glass fiber yarns using dip coating technique. Totally four types of hybridfibers were made with different MWNT weight percentages (0, 0.1, and 0.2). Tensile tests were carried out to examine the effect of MWNT coating on glass fiber on strength and stiffness of the hybridfibers. Further, the vibration damping of hybridfibers was evaluated using digital image correlation technique and noticed a remarkable improvement in damping ability. The fiber fractured surfaces were analyzed using field emission scanning electron microscope (FESEM). Furthermore, the hybrid fiber reinforced composites were prepared by reinforcing these hybridfibers in the epoxy matrix system for the 10% and 20% volume fractions. Tensile and compression tests were performed to evaluate the effect of hybridfibers role as reinforcement
Linear elastic fracture mechanics (LEFM)-based single lap joint (SLJ) mixed-mode analysis for aerospace structures}.
No full textThis paper investigates the study of crack propagation on single lap joint (SLJ) using cohesive zone modeling (CZM) for aerospace applications. To carry out the above task, linear elastic fracture mechanics (LEFM) approach using finite element methods was used to study the damage propagation in adhesively bonded joints. A traction–separation law was used to simulate the mode-II and mixed-mode-I+II interfacial fractures of adhesively bonded specimens loaded (quasi-static) in three-point bending and mixed-mode bending. An initial crack opening was introduced at the interfaces of the adherend/adhesive. The boundary conditions for SLJ have been set to carry out the interlaminar mode-II (shear mode) and mixed-mode fracture analysis by end notched flexure (ENF) and mixed-mode bending (MMB) methods. Optimized cohesive parameters from the literature survey were used for simulation of the tests, and same parameters have been validated to continue the research work focusing mainly on progressive delamination in SLJ. The total displacement of 10 mm was applied at free end, and as a result the reaction forces at fixed end steadily progressed up to 60% of applied displacement; further it has been observed the model starts failing by reduction in load versus displacement slope curve
Simulation and validation of disbond growth in co-cured composite skin–stringer specimens using cohesive elements
No full textSeparation of skin and stringer is likely to be a failure mode in co-cured composites stiffened panels where there isconsiderable out-of-plane deformation. Such deformations are possible when a stiffened skin structure is loaded incompression/shear beyond buckling or in structures which contain a disbond/delamination at the skin–stringer interface.Prediction of damage initiation and progressive growth in numerical simulations require parameters such as interfacefracture toughness which have to be obtained through specimen tests. Since interface toughness is generally modedependent, this study deals with the design and testing of three different configuration of blade stiffened co-curedcomposite skin–stringer specimens under mode-I and mode-II dominated loading. Finite element numerical modelsare developed using three-dimensional cohesive elements to predict the disbond growth under mode-I and mode-IIdominated loading. The work also addresses the complexities in the convergence of numerical simulations that arise dueto cohesive elements. A systematic way to obtain the best values for cohesive element parameters while finding a balancebetween accuracy of the results, computation time and numerical stability is presented. The present cohesive elementmodelling and analysis methodology successfully predicted the disbond growth in skin–stringer specimen and can be usedto predict disbond/delamination onset or growth in composite stiffened structures subjected to high bendin
Supercapacitor performance study of lithium chloride doped polyaniline.
No full textLithium chloride doped polyaniline (PAni-LiCl) has been synthesized for using as an electroactive material for supercapacitor application. The morphological studies have been carried out by using SEM and HR-TEM techniques, while thermal studies have been made through thermogravimetric analysis (TGA). Characterization of the surface composition of the PAni-LiCl have been performed using X-ray photoelectron spectroscopy (XPS). Electrochemical characterization was done by using cyclic voltammetry, galvanostatic charge-discharge and impedance spectroscopy measurements. The synthesized PAni-LiCl is subjected to electroanalytical technique to study the supercapacitor behavior. PAni-LiCl used as the electroactive material, could provide maximum specific capacitance of 395 F g−1 at a scan rate of 1 mV s−1 in 1 M H2SO4 as electrolyte obtained from cyclic voltammetry technique and the specific capacitance of PAni-LiCl measured by the galvanostatic charge-discharge curve at a current density of 1 A g−1 shows 471 F g−1 using the same electrolyte. PAni-LiCl is observed to yield a higher energy density and power density of 65.42 W h kg−1 and 178.57 W kg−1 respectively. 100% Columbic efficiency has been attained after 1000 cycles. The specific capacitance of 167.28 F g−1 could be obtained through impedance spectroscopy
Dye degradation studies of Mo-doped TiO2 thin films developed by reactive sputtering.
Get PDFTiO2 thin films with various Mo concentrations have been deposited on glass and n‐type silicon (100) substrates by this radio‐frequency (RF) reactive magnetron sputtering at 400°C substrate temperature. The crystal structure, surface morphology, composition, and elemental oxidation states of the films have been analyzed by using X‐ray diffraction, field emission scanning electron microscopy, atomic force microscopy, and X‐ray photoelectron spectroscopy, respectively. Ultraviolet‐visible spectroscopy has been used to investigate the degradation, transmittance, and absorption properties of doped and undoped TiO2 films. The photocatalytic degradation activity of the films was evaluated by using methylene blue under a light intensity of 100 mW cm−2. The X‐ray diffraction patterns show the presence of anatase phase of TiO2 in the developed films. X‐ray photoelectron spectroscopy studies have confirmed that Mo is present only as Mo6+ ions in all films. The Mo/TiO2 band gap decreases from ~3.3 to 3.1 eV with increasing Mo dopant concentrations. Dye degradation of ~60% is observed in Mo/TiO2 samples, which is much higher than that of pure TiO2
Influence of manufacturing parameters on the strength of PLA parts using Layered Manufacturing technique: A statistical approach
No full textA 3D printing was successfully used to fabricate samples of Polylactic Acid (PLA). Processing parameters such as Lay-up speed, Lay-up thickness, and printing nozzle were varied. All samples were tested for flexural strength using three point load test. A statistical mathematical model was developed to correlate the processing parameters with flexural strength. The result clearly demonstrated that the lay-up thickness and nozzle diameter influenced flexural strength significantly, whereas lay-up speed hardly influenced the flexural strength
Correlation of structural ordering with magnetic properties of pulsed laser deposited Co2FeGa Heusler alloy thin films
No full textIn the present contribution, structural and magnetic properties of Pulsed laser deposited (PLD) Co2FeGa (CFG) thin films have been studied as a function of substrate temperature. Structural investigation carried out by X-Ray Diffraction (XRD) measurement reveals mixed phase cubic structure of the films which changes from a nearly ordered to highly disordered phase with an increase in substrate temperature. Grazing Incidence X-Ray Diffraction (GIXRD) study shows the presence of disordered A2 phase similar to the bulk target. Grazing Incidence X-Ray Reflectivity (GIXR) measurement reveals the formation of bi-layer structure in the films with different density and thickness though the overall thickness remains same. Field Emission Scanning Electron Microscopy (FESEM) study shows the formation of a droplet-like morphology of the films. Extended X-ray Absorption Fine Structure (EXAFS) study serves a major role in complementing the XRD results and also shows a strong hybridization of Co with Ga maintaining the half metallicity. A novel approach in analyzing the EXAFS data additionally gives quantitative estimation of the different kinds of disorders present in the samples at the atomic level. In addition to this, magnetization result suggests that the films grown at lower substrate temperatures acts as proper ferromagnet following the well known spin wave theory with higher value of spontaneous magnetization in comparison to other samples. A lesser value of saturation magnetization in the films compared to bulk also supports the presence of antisite disorders