Browsing by Author "Zeltmann, S.E."

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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
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.
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.
Prediction of modulus at various strain rates from dynamic mechanical analysis data for polymer matrix composites
(Elsevier Ltd, 2017) Zeltmann, S.E.; Prakash, K.A.; Doddamani, M.; Gupta, N.
Understanding and modeling the behavior of polymers and composites at a wide range of quasi-static and high strain rates is of great interest to applications that are subjected to dynamic loading conditions. The Standard Linear Solid model or Prony series frameworks for modeling of strain rate dependent behavior are limited due to simplicity of the models to accurately represent a viscoelastic material with multiple relaxations. This work is aimed at developing a technique for manipulating the data derived from dynamic mechanical analysis to obtain an accurate estimate of the relaxation modulus of a material over a large range of strain rate. The technique relies on using the time-temperature superposition principle to obtain a frequency-domain master curve, and integral transform of this material response to the time domain using the theory of viscoelasticity. The relaxation function obtained from this technique is validated for two polymer matrix composites by comparing its predictions of the response to uniaxial strain at a prescribed strain rate to measurements taken from a separate set of tension experiments and excellent matching is observed. © 2017 Elsevier Ltd
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 Ltd
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.
Tensile behavior of compression molded glass microballoon/HDPE syntactic foams
(2016) Jayavardhan, M.L.; Bharath, Kumar, B.R.; Doddamani, M.; Zeltmann, S.E.; Gupta, N.
Tensile behavior of glass microballoon (GMB) reinforced high density polyethylene (HDPE) matrix syntactic foams is investigated in the present study. GMB's having true particle density 350 kg/m3 are varied in 0, 20, 40 and 60 by vol. % in HDPE matrix using brabender and subsequently compression molded to form the syntactic foam sheets. Experimental results show that the modulus increases while strength decreases with increase in microballoon content. Syntactic foams present lower fracture strain as compared to neat HDPE. For designing syntactic foam microstructures with desired properties theoretical model can be effectively utilized.
Tensile behavior of compression molded glass microballoon/HDPE syntactic foams
(DEStech Publications Inc. info@destechpub.com, 2016) Jayavardhan, M.L.; Bharath Kumar, B.R.; Doddamani, M.; Zeltmann, S.E.; Gupta, N.
Tensile behavior of glass microballoon (GMB) reinforced high density polyethylene (HDPE) matrix syntactic foams is investigated in the present study. GMB's having true particle density 350 kg/m3 are varied in 0, 20, 40 and 60 by vol. % in HDPE matrix using brabender and subsequently compression molded to form the syntactic foam sheets. Experimental results show that the modulus increases while strength decreases with increase in microballoon content. Syntactic foams present lower fracture strain as compared to neat HDPE. For designing syntactic foam microstructures with desired properties theoretical model can be effectively utilized.
Testing of foams
(Springer Singapore, 2019) Gupta, N.; Zeltmann, S.E.; Luong, D.D.; Doddamani, M.
Foams are lightweight cellular materials that are widely used in applications such as packaging, thermal insulation, sound absorption, underwater vehicle structures, and as the core in sandwich structures used in aircraft. Testing of foams to obtain reliable properties that are relevant to a given application is a significant challenge. High damping, high compressive or tensile strain, and high volume of air in the structure are among the challenges that make it difficult to apply the common test methods to these materials. For example, use of strain gauges for tensile or compression testing is usually not possible because bonding the strain gauges to the surface of a cellular material may not be possible, the small measurement range of a strain gauge may not be enough to capture the strain in the entire loading range, and microscopic material structure may dominate the measurement. This chapter discusses test techniques that include quasi-static compression, high strain rate compression, impact, dynamic mechanical analysis, vibration methods, and imaging techniques that are relevant to testing of foams. The imaging methods include ultrasonic imaging and microCT-scanning. Test techniques are described and results on representative foam materials are presented to understand the test outcomes. © Springer Nature Singapore Pte Ltd. 2019.