Browsing by Author "Gupta, N."

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3D printing of fly ash-based syntactic foams
(Elsevier, 2021) Doddamani, M.; Gupta, N.
In addition to the ease of fabrication using a wide range of forming processes, thermoplastic polymers are recyclable, which is a strong driving force behind their industrial applications. This chapter deals with manufacturing thermoplastic matrix lightweight composites called syntactic foams (SFs) using in the fused filament fabrication 3D printing process. High-density polyethylene (HDPE) is used as the matrix material and fly ash cenospheres are used as the filler. The development of SFs with cenospheres serves a dual purpose of beneficial utilization of industrial waste fly ash and a reduction in the component cost. Hollow fly ash cenospheres are mixed with HDPE to form a cenosphere/HDPE blend, which is extruded in the form of filaments for commercial 3D printers. Single-screw extruder parameters are optimized to develop eco-friendly SF filaments with minimum cenosphere fracture and homogeneous mixing of constituents. Fly ash-based SFs are successfully 3D printed for mechanical characterization and their properties are observed to be comparable to injection molded specimens of the same compositions. 3D printing of industrial components is successfully demonstrated with potential weight saving capabilities of 8% in addition to reduced polymer consumption to the tune of 4.64 million tons globally per year. © 2022 Elsevier Inc. All rights reserved.
3D Printing of Syntactic Foams for Marine Applications
(Springer International Publishing, 2020) Gupta, N.; Doddamani, M.
Syntactic foams are hollow particle filled lightweight composite materials that are widely used in structural applications in underwater marine vessels. Additive manufacturing (AM), also called 3D printing, methods are now being developed for printing parts of syntactic foams. These methods provide advantage that the entire part can be printed without the requirement of machining or joining and eliminates stress concentration locations. The present work is focused on describing the method of creating a syntactic foam filament for fused filament fabrication type printers and then developing parameters for printing syntactic foams parts using commercial printers. High density polyethylene resin is used as the matrix material with fly ash cenospehres and hollow glass microballoons as the fillers for creating syntactic foams. One of the major challenges is to minimize the fracture of hollow particles during filament manufacturing and 3D printing, which is addressed by parameter optimization during processing. Results show that the syntactic foam specimens are successfully printed and their properties are comparable to the injection molded specimens of the same compositions. © Springer Nature Switzerland AG 2020.
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.
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.
Additive Manufacturing of Three-Phase Syntactic Foams Containing Glass Microballoons and Air Pores
(Minerals, Metals and Materials Society 184 Thorn Hill Road Warrendale PA 15086, 2019) Singh, A.K.; Deptula, A.J.; Anawal, R.; Doddamani, M.; Gupta, N.
High-density polyethylene and its syntactic foams reinforced with 20 vol.% and 40 vol.% glass microballoons were 3D printed using the fused filament fabrication method and studied for their compressive response. The three-phase microstructure of syntactic foams fabricated in this work also contained about 10 vol.% matrix porosity for obtaining light weight for buoyancy applications. Filaments for 3D printing were developed using a single screw filament extruder and printed on a commercial 3D printer using settings optimized in this work. Three-dimensional printed blanks were machined to obtain specimens that were tested at 10 ?4 s ?1 , 10 ?3 s ?1 , 10 ?2 s ?1 and 1 s ?1 strain rates. The compression results were compared with those of compression-molded (CM) specimens of the same materials. It was observed that the syntactic foam had a three-phase microstructure: matrix, microballoons and air voids. The air voids made the resulting foam lighter than the CM specimen. The moduli of the 3D-printed specimen were higher than those of the CM specimens at all strain rates. Yield strength was observed to be higher for CM samples than 3D-printed ones. © 2019, The Minerals, Metals & Materials Society.
Batch and continuous studies on the removal of heavy metals from aqueous solution using biosynthesised melanin-coated PVDF membranes
(Springer, 2020) Manirethan, V.; Gupta, N.; Mohan Balakrishnan, R.M.; Raval, K.
Heavy metals like mercury, chromium, lead and copper present in groundwater at lower concentrations cause severe health issues and can even be fatal when consumed. The biopigment/biopolymer melanin can be reaped from different sources like bacterium, fungus, and human hair. It has excellent heavy metal ion scavenging property and can be exploited for non-biological applications, substantially including water purification. In this work, melanin nanoparticles were derived from the marine bacterium Pseudomonas stutzeri and were coated onto hydrophobic polyvinylidene fluoride (PVDF) membrane as a support, for batch and continuous removal of heavy metal studies. Batch studies on the effect of pH, temperature and adsorbate dose and continuous adsorption studies on the effect of flow rate, adsorbate and adsorbent mass loadings were carried out by using biosynthesised melanin-coated PVDF membranes for the removal of Hg(II), Cr(VI), Pb(II) and Cu(II). Scanning electron microscope (SEM) images revealed the surface morphology, Fourier-transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDS) deciphered the chemical characteristics of melanin-coated PVDF membranes before and after adsorption. Contact angle measurement confirmed the improvement in hydrophilicity of PVDF membrane upon coating with melanin. The maximum removal percentages of heavy metals achieved by melanin-coated PVDF membranes under batch mode operation were 87.6%, 88.45%, 91.8% and 95.8% for mercury, chromium, lead and copper, respectively optimised at 318 K and pH of 3 for chromium and 5 for other metals. However, the continuous mode of operation with a flow rate of 0.5 mL/min having 1 mg/L of heavy metal solution concentration exposed to 50 mg of melanin loading with a working volume of 200 mL showed better removal efficiencies compared with batch mode. The dynamic studies using Thomas and Yoon–Nelson models described the transient stage of the breakthrough curve and the model constants were calculated for column design and scale-up. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.
Buckling and free vibration behavior of cenosphere/epoxy syntactic foams under axial compressive loading
(ASTM International, 2018) Waddar, S.; Jeyaraj, P.; Doddamani, M.; Gupta, N.
The buckling and free vibration behavior of cenosphere/epoxy syntactic foams under axial compressive loading are investigated experimentally in this work. The buckling load is obtained from the load-deflection curve based on the Double Tangent Method (DTM) and Modified Budiansky Criteria (MBC). Furthermore, the influence of an axial compression load on the natural frequencies associated with the first three transverse bending modes is analyzed. Finally, the buckling loads predicted using DTM and MBC are compared to the buckling load calculated based on the vibration correlation technique. It is observed that the buckling loads predicted through the three different methods are in close agreement. The experimental results revealed that the buckling load and natural frequency of the syntactic foams increase with the cenosphere volume fraction. It is observed that the natural frequencies reduce with increases in the axial compression load for all the modes. However, a rapid increase in the fundamental frequency is observed when the compressive load is near and beyond the critical buckling load. © © 2018 by ASTM International.
Compressive and flexural properties of functionally graded fly ash cenosphere-epoxy resin syntactic foams
(John Wiley and Sons Inc, 2015) Doddamani, M.; Kishore; Shunmugasamy, V.C.; Gupta, N.; Vijayakumar, H.B.
The present study focuses on developing functionally graded syntactic foams (FGSFs) based on a layered co-curing technique. The FGSFs were characterized for compressive and flexural properties and compared with plain syntactic foams. The results showed that the specific compressive modulus was 3-67% higher in FGSFs compared to plain syntactic foams. FGSF exhibited 5-34% and 34-87% higher specific modulus and strength, respectively in flexural mode. The microscopic examinations of comparative responses of the filler and matrix to deformation suggest that the failure is dominated by the matrix. The gradient in the composition of syntactic foams helps in effectively distributing the stress throughout the microstructure and results in improved mechanical performance of syntactic foams. From the microscopy studies, it is evident that, the failure mechanism in the FGSF under flexural loading is governed by a crack that initiated on the tensile side of the specimen and propagated through the thickness to cause complete fracture. The microscopic observations further clearly demonstrate the existence of seamless interfaces between the layers and a clear difference in the cenosphere concentration across the interface, affirming the gradation in the prepared samples. The results show that appropriate compositions of FGSFs can be selected to develop materials with improved mechanical performance. © 2014 Society of Plastics Engineers.
Compressive behavior of cenosphere/hdpe syntactic foams under different strain rates
(2016) Kumar, B.R.B.; Singh, A.K.; Doddamani, M.; D, Luong, D.; Gupta, N.
An industrial scale injection molding machine is used to prepare fly ash cenosphere reinforced high density polyethylene (HDPE) syntactic foams. Thermosetting matrix foams with glass microspheres are being used in marine and aerospace applications owing to higher specific properties. Thermoplastic matrix syntactic foams have not been studied extensively despite interest in them for lightweight underwater vehicle structures and consumer products. Syntactic foams are fabricated with 20 and 40% cenospheres by weight. The studies on the manufacturing process suggest that a small percentage of cenospheres fracture in syntactic foams containing up to 40 wt.% cenospheres. Incorporation of particles, which are inexpensive, helps in fabricating low cost syntactic foams. Quasi-static compression tests are conducted at 10-4, 10-3 and 10-2 s-1 strain rates. The compressive strength of syntactic foams is higher than that of HDPE resin at the same strain rate due to the incorporation of ceramic particles. Yield strength shows an increasing trend with strain rate.
Compressive behavior of cenosphere/hdpe syntactic foams under different strain rates
(DEStech Publications Inc. info@destechpub.com, 2016) Kumar, B.R.B.; Singh, A.K.; Doddamani, M.; D Luong, D.; Gupta, N.
An industrial scale injection molding machine is used to prepare fly ash cenosphere reinforced high density polyethylene (HDPE) syntactic foams. Thermosetting matrix foams with glass microspheres are being used in marine and aerospace applications owing to higher specific properties. Thermoplastic matrix syntactic foams have not been studied extensively despite interest in them for lightweight underwater vehicle structures and consumer products. Syntactic foams are fabricated with 20 and 40% cenospheres by weight. The studies on the manufacturing process suggest that a small percentage of cenospheres fracture in syntactic foams containing up to 40 wt.% cenospheres. Incorporation of particles, which are inexpensive, helps in fabricating low cost syntactic foams. Quasi-static compression tests are conducted at 10-4, 10-3 and 10-2 s-1 strain rates. The compressive strength of syntactic foams is higher than that of HDPE resin at the same strain rate due to the incorporation of ceramic particles. Yield strength shows an increasing trend with strain rate.
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 Ltd
Dry sliding wear of epoxy/cenosphere syntactic foams
(Elsevier Ltd, 2015) Manakari, V.; Parande, G.; Doddamani, M.; Gaitonde, V.N.; Siddhalingeshwar, I.G.; Kishore; Shunmugasamy, V.C.; Gupta, N.
Abstract Dry sliding wear behavior of epoxy matrix syntactic foams filled with 20, 40 and 60 wt% fly ash cenosphere is reported based on response surface methodology. Empirical models are constructed and validated based on analysis of variance. Results show that syntactic foams have higher wear resistance than the matrix resin. Among the parameters studied, the applied normal load (F) had a prominent effect on wear rate, specific wear rate (ws) and coefficient of friction (?). With increasing F, the wear rate increased, whereas ws and ? decreased. With increase in filler content, the wear rate and ws decreased, while the ? increased. With increase in sliding velocity as well as sliding distance, the wear rate and ws show decreasing trends. Microscopy revealed broken cenospheres forming debris and extensive deformation marks on the wear surface. © 2015 Elsevier Ltd.
Dynamic mechanical analysis of cenosphere/hdpe syntactic foams
(2016) Zeltmann, S.E.; Gupta, N.; Kumar, B.R.B.; Doddamani, M.
High density polyethylene (HDPE) syntactic foams containing fly ash cenospheres as the hollow filler are fabricated using an industrial scale injection molding machine and studied for their dynamic mechanical behavior. Syntactic foams using thermoset matrix materials and engineered glass hollow particles have long been used as buoyancy devices and thermal insulation in the marine sector and as a lightweight sandwich core in the aerospace industry. This class of materials is attractive because of high mechanical properties in compression, tailorable density, and improved thermal properties. The constituents are used in as-received condition, without surface treatments. These lightweight composites can be highly beneficial in developing consumer goods by reducing consumption of HDPE. Syntactic foams are produced containing 20, 40, and 60% cenospheres by weight. A temperature sweep from 35-130�C and a frequency sweep from 1-100 Hz are conducted on the fabricated syntactic foams. At all temperatures, syntactic foams show higher storage and loss moduli and lower damping than neat HDPE. Syntactic foams with 60 wt.% cenospheres show only a small increase in properties compared to those with 40 vol.% due to particle breakage during processing. However, high particle loading has the benefit of reducing consumption of HDPE. The time-temperature superposition principle is used to extend the frequency response to cover the range 10-2-106 Hz.
Dynamic mechanical analysis of cenosphere/hdpe syntactic foams
(DEStech Publications Inc. info@destechpub.com, 2016) Zeltmann, S.E.; Gupta, N.; Kumar, B.R.B.; Doddamani, M.
High density polyethylene (HDPE) syntactic foams containing fly ash cenospheres as the hollow filler are fabricated using an industrial scale injection molding machine and studied for their dynamic mechanical behavior. Syntactic foams using thermoset matrix materials and engineered glass hollow particles have long been used as buoyancy devices and thermal insulation in the marine sector and as a lightweight sandwich core in the aerospace industry. This class of materials is attractive because of high mechanical properties in compression, tailorable density, and improved thermal properties. The constituents are used in as-received condition, without surface treatments. These lightweight composites can be highly beneficial in developing consumer goods by reducing consumption of HDPE. Syntactic foams are produced containing 20, 40, and 60% cenospheres by weight. A temperature sweep from 35-130Â°C and a frequency sweep from 1-100 Hz are conducted on the fabricated syntactic foams. At all temperatures, syntactic foams show higher storage and loss moduli and lower damping than neat HDPE. Syntactic foams with 60 wt.% cenospheres show only a small increase in properties compared to those with 40 vol.% due to particle breakage during processing. However, high particle loading has the benefit of reducing consumption of HDPE. The time-temperature superposition principle is used to extend the frequency response to cover the range 10-2-106 Hz.
Educational computing for the blind in India: Design, development and learning impact
(2012) Gupta, N.; Raghavan, A.; Shanbhogue, M.; Jain, A.
The aim of this paper is to present software engineering methodologies that were employed in developing educational solutions for the visually impaired. Empirical studies and experiments were conducted to measure the impact of the educational tools on the learning and cognitive abilities of the target user group. This study highlights the various technological and design challenges that were faced while developing and deploying these customized learning solutions. Observations and results indicate that there is significant merit in developing and utilizing such applications for the educational empowerment of the blind. � 2012 IEEE.
Educational computing for the blind in India: Design, development and learning impact
(2012) Gupta, N.; Raghavan, A.; Shanbhogue, M.; Jain, A.
The aim of this paper is to present software engineering methodologies that were employed in developing educational solutions for the visually impaired. Empirical studies and experiments were conducted to measure the impact of the educational tools on the learning and cognitive abilities of the target user group. This study highlights the various technological and design challenges that were faced while developing and deploying these customized learning solutions. Observations and results indicate that there is significant merit in developing and utilizing such applications for the educational empowerment of the blind. Â© 2012 IEEE.
Effect of cenosphere filler surface treatment on the erosion behavior of epoxy matrix syntactic foams
(John Wiley and Sons Inc. cs-journals@wiley.com, 2019) Shahapurkar, K.; Doddamani, M.; Mohan Kumar, G.C.; Gupta, N.
Influence of cenosphere surface modification and volume fraction on the solid particle erosion of cenosphere/epoxy syntactic foams is investigated. Fly ash cenospheres are used as filler in both as received and silane surface modified configurations. Erosion behavior is studied at room temperature for different impact angles (30, 45, 60, and 90°) and velocities (30, 45, and 60 m/s). Neat epoxy shows the highest erosion rate compared with that of the syntactic foams. Results show a strong dependence of impact angle and velocity on erosion rate of syntactic foams. With increasing cenosphere content erosion rate decreases for all impact angles. Erosion rate decreases with increasing impact angle and with decreasing velocity. Good interfacial bonding of treated cenospheres enhances the erosion resistance. All the samples exhibit ductile erosive behavior, with maximum erosion at 30°. The velocity exponent and erosion efficiency parameters confirm the ductile behavior of syntactic foams. POLYM. COMPOS., 40:2109–2118, 2019. © 2018 Society of Plastics Engineers. © 2018 Society of Plastics Engineers
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.
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.
Extracting elastic modulus at different strain rates and temperatures from dynamic mechanical analysis data: A study on nanocomposites
(Elsevier Ltd, 2019) Xu, X.; Koomson, C.; Doddamani, M.; Behera, R.K.; Gupta, N.
Viscoelastic nature of polymers makes their properties strongly dependent on temperature and strain rate. Characterization of material properties over a wide range of strain rates and temperatures requires an expensive and time consuming experimental campaign. While viscoelastic properties of materials are widely tested using dynamic mechanical analysis (DMA) method, the frequency dependent component of the measured properties is underutilized due to a lack of correlation between frequency, temperature, and strain rate. The present work develops a method that can extract elastic modulus over a range of strain rates and temperatures from the DMA data for nanocomposites. Carbon nanofiber (CNF) reinforced high-density polyethylene (HDPE) matrix nanocomposites are taken as the study material. Four different compositions of CNF/HDPE nanocomposites are tested using DMA from 40 to 120 °C at 1–100 Hz frequency. First, time-temperature superposition (TTS) principle is used to develop an extrapolation for the results beyond the test parameter range. Then the TTS curve is transformed to a time domain relaxation function using integral relations of viscoelasticity. Finally, the strain rate sensitive elastic modulus is extracted and extrapolated to room temperature. The transform results are validated with tensile test results and the error found to be below 13.4% in the strain rate range 10?5 to 10?3 for all four nanocomposites. Since the materials are tested with the aim of finding a correlation among the test methods, the quality of the material is not a study parameter and the transform should yield accurate results for any material regardless of composition and quality. © 2018 Elsevier Ltd