Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
32 results
Search Results
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 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.Item Prediction of strain rate sensitivity of high density polyethylene using integral transform of dynamic mechanical analysis data(Elsevier Ltd, 2016) Zeltmann, S.E.; Bharath Kumar, B.R.; Doddamani, M.R.; Gupta, N.Recent interest in understanding the effect of strain rate on mechanical properties has motivated this study to develop a correlation between frequency domain dynamic mechanical analysis (DMA) results and elastic modulus values that are obtained from a separate set of elaborate tensile tests conducted over a wide range of strain rates. Using the time-temperature superposition principle and the integral relations of viscoelasticity, the DMA results are converted into a time-domain relaxation function in order to predict the strain-rate dependent modulus. The transformation technique is validated with experimental results for high density polyethylene (HDPE) resin and is found to be accurate over a wide range of strain rates. Cross correlation between DMA results and tensile test results over a wide range of strain rates can help in substantially reducing the requirement for tests that are needed to characterize the material behavior with respect to strain rates, temperature and loading frequency. © 2016 Elsevier LtdItem Neutron radiation shielding properties of polymer incorporated self compacting concrete mixes(Elsevier Ltd, 2017) Malkapur, S.M.; Divakar, L.; Narasimhan, M.C.; Karkera, N.B.; Goverdhan, P.; Sathian, V.; Prasad, N.K.In this work, the neutron radiation shielding characteristics of a class of novel polymer-incorporated self-compacting concrete (PISCC) mixes are evaluated. Pulverized high density polyethylene (HDPE) material was used, at three different reference volumes, as a partial replacement to river sand in conventional concrete mixes. By such partial replacement of sand with polymer, additional hydrogen contents are incorporated in these concrete mixes and their effect on the neutron radiation shielding properties are studied. It has been observed from the initial set of experiments that there is a definite trend of reductions in the neutron flux and dose transmission factor values in these PISCC mixes vis-à-vis ordinary concrete mix. Also, the fact that quite similar enhanced shielding results are recorded even when reprocessed HDPE material is used in lieu of the virgin HDPE attracts further attention. © 2017 Elsevier LtdItem Development of glass microballoon/HDPE syntactic foams by compression molding(Elsevier Ltd, 2017) Jayavardhan, M.L.; Bharath Kumar, B.R.; Doddamani, M.; Singh, A.K.; Zeltmann, S.E.; Gupta, N.Thermoplastic resins are widely used in consumer products and industrial components. There is a significant interest in weight reduction of many of those components. Although glass hollow particle filled lightweight syntactic foams with thermoset matrices have been studied in detail, studies on thermoplastic syntactic foams are scarce. The present study is focused on developing a compression molding based processing method for glass microballoon/high density polyethylene (GMB/HDPE) syntactic foams and studying their mechanical properties to develop structure-property correlations. Blending of GMB in HDPE is carried out using a Brabender mixer with processing parameters optimized for minimal filler breakage. Flexural and tensile test specimens are compression molded with 20, 40 and 60 vol% of GMB. Particle fracture increases with increasing GMB content due to increased particle to particle interaction during processing. Additionally, increasing wall thickness makes GMBs stronger and results in reduced particle fracture. Flexural modulus increases while strength decreases with increasing filler content. Tensile strength decreases with increasing filler content, while tensile modulus is relatively unchanged. GMB volume fraction has a more prominent effect than the wall thickness on the mechanical properties of syntactic foams. Specific moduli of GMB/HDPE foams are superior while specific strength is comparable to neat HDPE. © 2017 Elsevier LtdItem Fresh and hardened properties of polymer incorporated self compacting concrete mixes for neutron radiation shielding(Elsevier Ltd, 2017) Malkapur, S.M.; Divakar, L.; Narasimhan, M.C.; Karkera, N.B.; Goverdhan, P.; Sathian, V.; Prasad, N.K.Several works in the past have reported that the hydrogen content in the hydrated concrete plays an important role in shielding the neutron radiation; higher the hydrogen content, better is the neutron radiation shielding. In this study, pulverised high density polyethylene (HDPE) material is used as an additional source of hydrogen within concrete to develop a novel class of Polymer-Incorporated Self-Compacting Concrete (PISCC) mixes for enhanced neutron radiation shielding. The HDPE material was incorporated as a partial replacement to river sand. It is found that the PISCC mixes have satisfactory fresh and hardened properties and enhanced neutron radiation shielding properties. © 2017 Elsevier LtdItem Additive Manufacturing of Syntactic Foams: Part 2: Specimen Printing and Mechanical Property Characterization(Minerals, Metals and Materials Society 184 Thorn Hill Road Warrendale PA 15086, 2018) Singh, A.K.; Saltonstall, B.; Patil, B.; Hoffmann, N.; Doddamani, M.; Gupta, N.High-density polyethylene (HDPE) and its fly ash cenosphere-filled syntactic foam filaments have been recently developed. These filaments are used for three-dimensional (3D) printing using a commercial printer. The developed syntactic foam filament (HDPE40) contains 40 wt.% cenospheres in the HDPE matrix. Printing parameters for HDPE and HDPE40 were optimized for use in widely available commercial printers, and specimens were three-dimensionally (3D) printed for tensile testing at strain rate of 10?3 s?1. Process optimization resulted in smooth operation of the 3D printer without nozzle clogging or cenosphere fracture during the printing process. Characterization results revealed that the tensile modulus values of 3D-printed HDPE and HDPE40 specimens were higher than those of injection-molded specimens, while the tensile strength was comparable, but the fracture strain and density were lower. © 2018, The Minerals, Metals & Materials Society.Item Additive Manufacturing of Syntactic Foams: Part 1: Development, Properties, and Recycling Potential of Filaments(Minerals, Metals and Materials Society 184 Thorn Hill Road Warrendale PA 15086, 2018) Singh, A.K.; Patil, B.; Hoffmann, N.; Saltonstall, B.; Doddamani, M.; Gupta, N.This work focuses on developing filaments of high-density polyethylene (HDPE) and their hollow particle-filled syntactic foams for commercial three-dimensional (3D) printers based on fused filament fabrication technology. Hollow fly-ash cenospheres were blended by 40 wt.% in a HDPE matrix to produce syntactic foam (HDPE40) filaments. Further, the recycling potential was studied by pelletizing the filaments again to extrude twice (2×) and three times (3×). The filaments were tensile tested at 10?4 s?1, 10?3 s?1, and 10?2 s?1 strain rates. HDPE40 filaments show an increasing trend in modulus and strength with the strain rate. Higher density and modulus were noticed for 2× filaments compared to 1× filaments because of the crushing of some cenospheres in the extrusion cycle. However, 2× and 3× filament densities are nearly the same, showing potential for recycling them. The filaments show better properties than the same materials processed by conventional injection molding. Micro-CT scans show a uniform dispersion of cenospheres in all filaments. © 2018, The Minerals, Metals & Materials Society.