Conference Papers

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Author: search.filters.author.Doddamani, M.

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    Tensile properties of cenosphere/HDPE syntactic foams manufactured using an industrial scale injection molding technique
    (DEStech Publications, 2015) Kumar, B.R.B.; Doddamani, M.; Gupta, N.
    Composite materials having hollow fillers in a matrix material are known as syntactic foams. Such lightweight composites are used in a variety of applications ranging from sports, transportation, aviation and marine structures due to high dimensional stability, compressive strength and low moisture absorption. The present work is focused on using an industrial scale injection molding technique for fabricating syntactic foams and characterizing the fabricated syntactic foams for tensile properties. Use of such techniques can help in developing foams with high quality for bulk applications. Hollow fly ash cenospheres are used as the filler particles due to their low cost. Use of these industrial waste particles in beneficial applications can also help in their disposal. The present work is aimed at characterizing syntactic foams for tensile properties and investigating the effect of filler content. The syntactic foam density can be changed by changing cenospheres content. Cenospheres in 20 and 60 wt.% are used in syntactic foams in the present work. ASTM D 638-10 standard for the tensile properties of unreinforced and reinforced plastics is followed for the tensile testing. © © 2015 by DEStech Publications, Inc. and American Society for Composites. All rights reserved.
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    Tribological response of cenosphere/epoxy syntactic foams
    (DEStech Publications, 2015) Manakari, V.; Parande, G.; Bafna, K.; Doddamani, M.; Gupta, N.
    Fly ash cenospheres are generated in thermal power plants as waste materials. Use of these waste materials in beneficial applications is desired. The present work deals with developing syntactic foams with fly ash cenospheres filled in epoxy resin matrix. Such syntactic foams can be used as core materials in sandwich composites. The fabricated syntactic foams are evaluated for dry sliding wear behavior. Sliding velocity and filler content were the study parameters, effects of which were analyzed on wear rate. Specimens were prepared with 10, 30 and 50 wt. % cenospheres for the study. Sliding against hardened ground steel on a pin-on disc wear testing machine was conducted. The experimental results and subsequent analysis showed that the addition of cenospheres as filler material in epoxy matrix considerably increases the wear resistance of the composites. The craters on the specimen surface due to presence of cenospheres play important role in the wear process. © © 2015 by DEStech Publications, Inc. and American Society for Composites. All rights reserved.
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    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.
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    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.
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    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 35-130°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.
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    Dynamic impact behavior of syntactic foam core sandwich composites
    (DEStech Publications Inc. info@destechpub.com, 2018) Breunig, P.; Damodaran, V.; Shahapurkar, K.; Waddar, S.; Doddamani, M.; Jeyaraj, P.; Mohan Kumar, G.C.M.; Prabhakar, P.
    Sandwich composites and syntactic foams have historically been used in many engineering applications to meet the needs of a system. However, there has been minimal effort to take advantage of the weight saving ability of syntactic foams in the cores of sandwich composites, especially with respect to the impact response of the structure. The goal of this experimental study is to investigate the mechanical response and damage mechanisms associated with sandwich composites with syntactic foam cores. The core was manufactured using epoxy resin as the matrix and cenospheres as the reinforcement with varying volume fractions of 0%, 20%, 40%, and 60%. The sandwich composites were manufactured with the vacuum assisted resin transfer molding (VARTM) process. Impact tests were performed on the specimens according to ASTM D7766 at two energy levels: 80J and 160J. The data from the tests was post-processed to gain quantitative understanding of the damage mechanisms present in the specimens. A qualitative understanding was obtained through MicroCT scanning imaging. The analysis showed that increasing the volume fraction of cenospheres in the syntactic foam made the damage mechanism more desirable, even at high energy levels. © 2018 by DEStech Publications, Inc. All rights reserved..
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    Evaluation of circularity error in drilling of syntactic foam composites
    (American Institute of Physics Inc. subs@aip.org, 2018) Ashrith, H.S.; Doddamani, M.; Gaitonde, V.
    Syntactic foams are widely used in structural applications of automobiles, aircrafts and underwater vehicles due to their lightweight properties combined with high compression strength and low moisture absorption. Structural application requires drilling of holes for assembly purpose. In this investigation response surface methodology based mathematical models are used to analyze the effects of cutting speed, feed, drill diameter and filler content on circularity error both at entry and exit level in drilling of glass microballoon reinforced epoxy syntactic foam. Experiments are conducted based on full factorial design using solid coated tungsten carbide twist drills. The parametric analysis reveals that circularity error is highly influenced by drill diameter followed by spindle speed at the entry and exit level. Parametric analysis also reveals that increasing filler content decreases circularity error by 13.65 and 11.96% respectively at entry and exit levels. Average circularity error at the entry level is found to be 23.73% higher than at the exit level. © 2018 Author(s).
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    Experimental investigation on stability and dynamic behaviour of laminated composite beam
    (American Institute of Physics Inc. subs@aip.org, 2018) Waddar, S.; Jeyaraj, P.; Doddamani, M.
    Experimental investigations carried out to analyze the effect of axial compression on buckling and dynamic behaviour of laminated composite beam is presented. Typical load vs deflection curve for the composite beam under axial compression load is used to evaluate the critical buckling load. Followed by this, the axial compression load is varied in fraction of critical buckling load and corresponding variation in first three transverse bending natural frequencies are analyzed. Influence of uni-directional, bi-directional and pre-preg reinforcement on buckling and natural frequencies also studied. It is found that buckling strength of the pre-preg composite beam is significantly higher than the other two types of beam studied. It is also observed that increase in axial compression load reduces natural frequencies of the beam and the effect is significant for the fundamental mode. © 2018 Author(s).
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    Tensile behavior of cenosphere/epoxy syntactic foams
    (American Institute of Physics Inc. subs@aip.org, 2018) Shahapurkar, K.; Doddamani, M.; Mohan Kumar, G.C.
    Tensile behavior of syntactic foam composites are very critical to the engineering applications. The fracture modes and failure mechanisms under tension must be fully understood in order to realize the potential of such composites. In the present work, syntactic foam composites are fabricated using as received and surface modified hollow cenospheres embedded into epoxy matrix. Combinations of cenosphere volume fraction (0, 20, 40 and 60%) and surface modification are studied. Experimental results reveal that modulus of both untreated and treated syntactic foams increases with increase in cenosphere volume fraction compared to neat resin. Strength values of syntactic foams show decreasing trend compared to neat resin. However, treated syntactic foams demonstrated better results compared to untreated ones attributing to good bonding between matrix and filler. Scanning electron microscopy reveal brittle fracture for all the syntactic foams. © 2018 Author(s).
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    Cyclic oxidation behavior of plasma sprayed NiCrAlY/WC-Co/cenosphere coating
    (American Institute of Physics Inc. subs@aip.org, 2018) Mathapati, M.; Ramesh, M.R.; Doddamani, M.
    Components working at elevated temperature like boiler tubes of coal and gas fired power generation plants, blades of gas and steam turbines etc. experience degradation owing to oxidation. Oxidation resistance of such components can be increased by developing protective coatings. In the present investigation NiCrAlY-WC-Co/Cenosphere coating is deposited on MDN 321 steel substrate using plasma spray coating. Thermo cyclic oxidation behavior of coating and substrate is studied in static air at 600 °C for 20 cycles. The thermo gravimetric technique is used to approximate the kinetics of oxidation. X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS) and X-ray mapping techniques are used to characterize the oxidized samples. NiCrAlY-WC-Co/Cenosphere coating exhibited lower oxidation rate in comparison to MDN 321 steel substrate. The lower oxidation rate of coating is attributed to formation of Al2O3, Cr2O3, NiO and CoWO4 oxides on the outermost surface. © 2018 Author(s).