Faculty Publications
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Item 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.Item 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.Item 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.Item Metal Matrix Syntactic Composites(Elsevier, 2021) Manakari, V.; Parande, G.; Gupta, M.; Doddamani, M.Syntactic foams have attracted considerable attention in recent years due to their potential for weight saving in packaging, armours, and vehicle structures. Metal matrix syntactic foams (MMSFs) are lightweight closed-cell composite foams produced by reinforcing hollow particles in the metal matrix. MMSFs can be synthesized with mechanical properties high enough to enable them to be used for load-bearing applications, raising the possibilities of structural weight reduction in numerous applications. Significant research efforts have been carried out on Mg, Al, Pb, Zn, Ti, Ni, Fe, and Invar matrix syntactic foams in recent years to tailor and enhance mechanical properties based on end applications. The present chapter reviews the recent state of the art in metal matrix syntactic foams and presents the fundamentals of structure-property correlations for syntactic foamsand synthesis methods that aid in developing multifunctionality in these composites. This chapter also reviews the weight saving ability of metal matrix syntactic foams and their potential scope and applications. © 2021 Elsevier Ltd. All rights reserved.Item Tribological Response of Magnesium/Glass Microballoon Syntactic Foams(Springer Science and Business Media Deutschland GmbH, 2022) Manakari, V.; Parande, G.; Doddamani, M.; Srivatsan, T.S.; Gupta, M.Magnesium (Mg)-based materials have great potential to replace the existing aluminum alloys and steels used in applications spanning the industries of defense, aerospace, and automotive due in essence to their excellent specific strength [σ/ρ], damping characteristics, and impact resistance. In this research study, we design an ultralow density magnesium/glass microballoon (GMB) syntactic foam having a density of 1.47 g/cc using the technique of Disintegrated Melt Deposition (DMD). The resultant material offered a healthy combination of extraordinary properties outperforming the existing aluminium and iron syntactic foams in terms of a noticeable improvement in specific strength [σ/ρ]. Further, the wear resistance of magnesium under dry sliding conditions showed a significant enhancement (~2.5 times) following the addition of glass microballoon (GMB). Abrasion and oxidation were identified to be the dominant wear mechanisms post worn-surface analysis. Morphology of the worn specimen provided clean, clear, and convincing evidence for the occurrence of delamination wear, which has traditionally limited the competitive advantage of magnesium and its alloy counterparts for selection and use in safety–critical components in transportation vehicles. This can be effectively overcome by the development of the proposed syntactic foams, which provide a unique cushioning effect against the applied load. © 2022, The Minerals, Metals & Materials Society.Item Lightweight and sustainable materials for coating applications(Elsevier, 2023) Mathapati, M.; Ramesh, M.R.; Doddamani, M.This chapter deals with the development of Cr3C2-25NiCr/cenosphere/MoS2/CaF2, Cr3C2-25NiCr/cenosphere/MoS2/CaSO4, and Cr3C2-25NiCr coatings through plasma spraying on MDN 321 steel substrate. Methods such as X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive spectroscopy (EDS) are used for coating phase composition and microstructure analysis. Sliding wear behavior of substrate and coatings is tested at 200°C-600°C by utilizing a pin-on-disk tribometer. Owing to the existence of cenospheres and action of solid lubricants, frictional coefficient and wear rate of fly ash cenosphere-based Cr3C2-25NiCr/MoS2/CaF2 and Cr3C2-25NiCr/MoS2/CaSO4 compositions are reduced in comparison with Cr3C2-25NiCr coating and substrate at all test parameters. The characterization of the coatings’ worn-out surface reveals lubrication at 200°C by MoS2. At elevated temperature, CaF2 with CaMoO4 formed through tribochemistry further aids lubrication. Micrographs of worn surfaces demonstrate plowing and delamination as the main wear mechanism. © 2023 Elsevier Ltd. All rights reserved.Item Thermal Buckling of 3D Printed Auxetic Core Sandwich Beams(Springer, 2025) Dattam, V.K.; Pitchaimani, J.; Doddamani, M.Experimental investigation carried out on the thermal deflection behavior of 3D printed poly lactic acid sandwich beams possessing positive, negative, and zero Poisson’s ratio cellular cores is presented. Using a fused deposition modelling based 3D printer, sandwich beams were fabricated and investigated for thermal buckling under different heating conditions. Influence of Poisson’s ratio of the core and orientation of the beam on thermal buckling were also studied. It is found that Poisson's ratio of the core influences the thermal deflection of the beams remarkably. The sandwich beam having a vertically oriented core with zero Poisson's ratio exhibited superior buckling resistance compared to the other two cases. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.Item Investigation on Corrosion Behavior of Polydimethylsiloxane and Nanofillers-Based Polymer Nanocomposite Coated Galvanized Iron(Springer, 2025) Kumar, P.; Kumar, S.; Ramesh, M.R.; Doddamani, M.The paper focuses on developing polydimethylsiloxane (PDMS) and nanofillers (ZnO and SiO2) based polymer nanocomposite solutions for coating galvanized iron (GI) using sol–gel dip coating method and investigating its corrosion behavior. The nanofillers in varying wt.% (0, 2, 4, 6, 8, and 10) are incorporated in the solution of PDMS and xylene for developing a nanocomposite coating solution. The solutions are characterized by pH, viscosity, and non-volatile matter. It is observed that all the solutions are basic. The viscosity (10.28–47.43%) and the non-volatile matter (8.06–15%) of the solutions are observed to be increasing with an increasing nanofiller % as compared to the base solution (PDMS and xylene). The developed solutions are coated on the GI substrate and tested for wettability, XRD, FTIR, and electrochemical responses. The wettability and the XRD tests confirm the hydrophobic and amorphous nature of the coated surface, respectively. The Si–O–Si groups are observed at 1088 cm−1. The electrochemical analysis shows that the impedance resistance of the coated surfaces is higher than that of the surface coated with the base solution. Further, the corrosion rate of the coated surfaces decreases with the % of the nanofillers. The coating with 10% nanofillers exhibited the highest impedance resistance and the lowest corrosion rate, finding applications in construction, marine, and naval. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.Item 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.Item 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.