Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
12 results
Search Results
Item Behavior of sandwich beams with functionally graded rubber core in three point bending(2011) Doddamani, M.R.; Kulkarni, S.M.; KishoreThe three-point bending behavior of sandwich beams made up of jute epoxy skins and piecewise linear functionally graded (FG) rubber core reinforced with fly ash filler is investigated. This work studies the influence of the parameters such as weight fraction of fly ash, core to thickness ratio, and orientation of jute on specific bending modulus and strength. The load displacement response of the sandwich is traced to evaluate the specific modulus and strength. FG core samples are prepared by using conventional casting technique and sandwich by hand layup. Presence of gradation is quantified experimentally. Results of bending test indicate that specific modulus and strength are primarily governed by filler content and core to sandwich thickness ratio. FG sandwiches with different gradation configurations (uniform, linear, and piecewise linear) are modeled using finite element analysis (ANSYS 5.4) to evaluate specific strength which is subsequently compared with the experimental results and the best gradation configuration is presented. © 2011 Society of Plastics Engineers.Item Instrumented ballistic performance of jute/epoxy sandwich with functionally graded rubber core(Inderscience Publishers, 2012) Doddamani, M.R.; Kulkarni, S.M.The qualitative analysis of instrumented ballistic impact for jute-epoxy sandwiches with fly ash reinforced functionally graded (FG) flexible, compliant rubber core is presented. An attempt is made to study the influence of fly ash weight fraction, jute orientation and core to total thickness (C/H) of sandwich on ballistic performance. Experiments are designed based upon L9 orthogonal array. Analysis of variance (ANOVA) is performed on recorded data to investigate the influence of parameters on ballistic response. An optimal parameter combination is determined leading to higher energy absorption and lower energy required for skin pullout by the bullet. A correlation derived from the results of Taguchi experimental design is proposed as a predictive equation for estimation of energy absorption of sandwiches. Furthermore, for arresting bullet optimum stack thickness of sandwich configuration is presented. Finally, the potential benefits for using such materials as a replacement for sand bags in guarding posts is highlighted. Copyright © 2012 Inderscience Enterprises Ltd.Item Response of fly ash-reinforced functionally graded rubber composites subjected to mechanical loading(2012) Doddamani, M.R.; Kulkarni, S.M.A novel approach to estimate the Young's modulus of a functionally graded rubber composite (FGRC) from the damping ratio is demonstrated with the examples of unreinforced and fly ash-reinforced materials. FGRC coupons were prepared using the conventional casting technique. The occurrence of gradation in the specimens was attributed to the variable density of particles present in the fly ash, settling at different depths. The technique of free vibrations was used for experimentation. The damping response of the FGRC specimens was studied. The results obtained from the experiments showed that, with growing filler weight fraction, the Young's modulus of the composite increased. The empirical model developed to predict the magnitude of the modulus turned out to be in good agreement with experimental data. © 2012 Springer Science+Business Media, Inc.Item Compressive properties of sandwiches with functionally graded rubber core and jute-epoxy skins(2013) Doddamani, M.R.; Kulkarni, S.The compressive behaviour of a new class of sandwich composite made up of jute fiber reinforced epoxy skins and piece-wise linear fly ash reinforced functionally graded (FG) rubber core is investigated in flat-wise mode. FG samples are prepared using conventional casting techniéue. Presence of gradation is éuantified physically by weight method. This paper addresses the effect of weight fraction of fly ash, core to thickness ratio (C/H) and orientation of jute on specific compressive modulus and strength. In each trial five replicates are tested with lower amount of fly ash below the upper skin of sandwich (rubber-up). Results of experimentation are subjected to statistical analysis of variance (ANOVA) to find the influential factor governing the compressive behaviour. Furthermore piece-wise linear gradation is modeled in finite element and strength values are compared with experimental results. Sandwich sample with fly ash content of 40%, C/H of 0.4 and orientations of 30?/60? registered better performance. Specific strength is observed to increase upto 30% filler content followed by stabilization. Finite element results for strength match very well with experimental ones.Item Electro-oxidation of nimesulide at 5% barium-doped zinc oxide nanoparticle modified glassy carbon electrode(Elsevier B.V., 2016) Bukkitgar, S.D.; Shetti, N.P.; Kulkarni, R.M.; Doddamani, M.R.Development of methods for the detection of an analyte at low concentration with less time for analysis has become a prior point of interest to every analyst. In reflection of this fact, an effort has been made to synthesize 5% barium doped zinc oxide nanoparticles and was characterized by using XRD, EDX, SEM, and TEM. Further, 5% barium doped zinc oxide nanoparticle modified glassy carbon electrode was used for investigating the electro-chemical behavior of nimesulide. Voltammograms obtained in a range of 3.0-11.2 (I = 0.2 M) pH had a maximum peak current at pH 7.0. Various physio-chemical parameters such as, process on the surface of the electrode, which was found to be diffusion controlled, heterogeneous rate constant, number of electrons transferred and charge transfer coefficient were estimated. Further, a method for nimesulide determination in a linear range of 1.0 × 10- 5 to 1.0 × 10- 7 M with LOD 1.794 nM was proposed. This technique was later used for analytical application. © 2015 Elsevier Ltd. All rights reserved.Item Processing of cenosphere/HDPE syntactic foams using an industrial scale polymer injection molding machine(Elsevier Ltd, 2016) Bharath Kumar, B.R.; Doddamani, M.R.; Zeltmann, S.E.; Gupta, N.; Ramesh, M.R.; Ramakrishna, S.Rapid production of high quality components is the key to cost reduction in industrial applications. The present work is the first attempt of manufacturing syntactic foams, hollow particle filled lightweight composites, using an industrial scale injection molding machine. High density polyethylene (HDPE) is used as the matrix material and fly ash cenospheres are used as the filler. Development of syntactic foams with cenospheres serves dual purpose of beneficial utilization of industrial waste fly ash and reduction in the cost of the component. The pressure and temperature used in the injection molding process are optimized to minimize fracture of cenospheres and obtain complete mixing of cenospheres with HDPE. The optimized parameters are used for manufacturing syntactic foams with 20, 40 and 60 wt.% cenospheres. With increasing cenosphere content, density and strength reduce and modulus increases. Surface modification of constituents results in rise in strength with increasing filler content. A theoretical model based on a differential scheme is used to estimate the properties of cenospheres by conducting parametric studies because of inherent difficulties in direct measurement of cenosphere properties. The potential for using the optimized injection molding process is demonstrated by casting several industrial components. © 2015 Elsevier Ltd.Item Effect of particle surface treatment and blending method on flexural properties of injection-molded cenosphere/HDPE syntactic foams(Springer New York LLC barbara.b.bertram@gsk.com, 2016) Bharath Kumar, B.R.; Doddamani, M.R.; Zeltmann, S.E.; Gupta, N.; Uzma; Gurupadu, S.; Sailaja, R.R.N.The present work on cenosphere/high-density polyethylene (HDPE) syntactic foams aims at understanding the effect of surface treatment of cenospheres and functionalization of HDPE on flexural properties. Cenospheres are treated with silane, and HDPE is functionalized with 10 % dibutyl maleate. Effects of mechanical and Brabender mixing methods are also studied. Flexural test specimens are cast with 20, 40, and 60 wt% of cenospheres using injection molding. The flexural modulus and strength are found to increase with increasing cenosphere content. Particle breakage increases with the cenosphere content, and the measured properties show increased dependence on processing method. Brabender mixing resulted in 70 and 41 % higher modulus and strength for 60 wt% cenospheres than HDPE. Modulus of syntactic foams is predicted by two theoretical models. Bardella–Genna model provides close estimates for syntactic foams having 20 and 40 wt% cenospheres, while predictions are higher for higher cenosphere content, likely due to particle breakage during processing. The uncertainty in the properties of cenospheres due to defects contributes to the variation in the predicted values. © 2015, Springer Science+Business Media New York.Item Quasi-Static and High Strain Rate Compressive Response of Injection-Molded Cenosphere/HDPE Syntactic Foam(Minerals, Metals and Materials Society 184 Thorn Hill Road Warrendale PA 15086, 2016) Bharath Kumar, B.R.; Singh, A.K.; Doddamani, M.R.; Luong, D.D.; Gupta, N.High strain rate compressive properties of high-density polyethylene (HDPE) matrix syntactic foams containing cenosphere filler are investigated. Thermoplastic matrix syntactic foams have not been studied extensively for high strain rate deformation response despite interest in them for lightweight underwater vehicle structures and consumer products. Quasi-static compression tests are conducted at 10?4 s?1, 10?3 s?1 and 10?2 s?1 strain rates. Further, a split-Hopkinson pressure bar is utilized for characterizing syntactic foams for high strain rate compression. The compressive strength of syntactic foams is higher than that of HDPE resin at the same strain rate. Yield strength shows an increasing trend with strain rate. The average yield strength values at high strain rates are almost twice the values obtained at 10?4 s?1 for HDPE resin and syntactic foams. Theoretical models are used to estimate the effectiveness of cenospheres in reinforcing syntactic foams. © 2016, The Minerals, Metals & Materials Society.Item Ag-TiO2 nanoparticles for photocatalytic degradation of lomefloxacin(Taylor and Francis Inc. 325 Chestnut St, Suite 800 Philadelphia PA 19106, 2016) Kulkarni, R.M.; Malladi, R.S.; Hanagadakar, M.S.; Doddamani, M.R.; Bhat, K.U.The photocatalytic activity of silver-doped TiO2 (Ag-TiO2) nanoparticles was studied by photocatalytic degradation of lomefloxacin (LMF) using a photoreactor with a mercury lamp (PHILIPS, TUV 8 W T5, Emax = 254 nm). The 1 and 2% silver-doped TiO2 nanoparticles were synthesized by liquid impregnation (LI) method. The resulting nanoparticles were characterized by surface analytical methods such as X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray analysis and transmission electron microscope (TEM). The study shows 2% Ag-TiO2 nanoparticles exhibited better results (95% degradation) in 1 h for the degradation of lomeofloxacin compared to 1% Ag-TiO2 and pure TiO2. XRD analysis indicated that the crystallite size of TiO2 was 17.00 nm, while the crystallite size of 1% Ag-TiO2 and 2% Ag-TiO2 was 13.07 to 14.17 nm. TEM images show the particle size of Ag-TiO2 nanoparticles were in the range 40–45 nm in length and 10–15 nm in breadth. Pseudo-first-order rate constants were found to decrease with increase in pH. The effect of UV intensity, catalyst dosage and initial concentration of LMF on the degradation rate were also studied and elaborately discussed. © 2015 Balaban Desalination Publications. All rights reserved.Item Effect of cenosphere surface treatment and blending method on the tensile properties of thermoplastic matrix syntactic foams(John Wiley and Sons Inc. P.O.Box 18667 Newark NJ 07191-8667, 2016) Bharath Kumar, B.R.; Zeltmann, S.E.; Doddamani, M.R.; Gupta, N.; Uzma; Gurupadu, S.; Sailaja, R.R.N.The influence of cenosphere surface treatment and blending method on the properties of injection molded high-density polyethylene (HDPE) matrix syntactic foams is investigated. Cenospheres are treated with silane and HDPE is functionalized with dibutyl maleate. Tensile test specimens are cast with 20, 40, and 60 wt % of cenospheres using injection molding. Modulus and strength are found to increase with increasing cenosphere content for composites with treated constituents. Highest modulus and strength were observed for 40 and 60 wt % untreated mechanically mixed and treated brabender mixed cenospheres/HDPE blends, respectively. These values are 37 and 17% higher than those for virgin and functionalized HDPE. Theoretical models are used to assess the effect of particle properties and interfacial bonding on modulus and strength of syntactic foams. Brabender mixing method provided highest ultimate tensile and fracture strengths, which is attributed to the effectiveness of Brabender in breaking particle clusters and generating the higher particle–matrix surface area compared to that by mechanical mixing method. Theoretical trends show clear benefits of improved particle–matrix interfacial bonding in the strength results. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43881. © 2016 Wiley Periodicals, Inc.