Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
10 results
Search Results
Item Enhancing the ignition, hardness and compressive response of magnesium by reinforcing with hollow glass microballoons(MDPI AG Postfach Basel CH-4005, 2017) Manakari, V.; Parande, G.; Doddamani, M.; Gupta, M.Magnesium (Mg)/glass microballoons (GMB) metal matrix syntactic foams (1.47-1.67 g/cc) were synthesized using a disintegrated melt deposition (DMD) processing route. Such syntactic foams are of great interest to the scientific community as potential candidate materials for the ever-changing demands in automotive, aerospace, and marine sectors. The synthesized composites were evaluated for their microstructural, thermal, and compressive properties. Results showed that microhardness and the dimensional stability of pure Mg increased with increasing GMB content. The ignition response of these foams was enhanced by -22 °C with a 25 wt % GMB addition to the Mg matrix. The authors of this work propose a new parameter, ignition factor, to quantify the superior ignition performance that the developed Mg foams exhibit. The room temperature compressive strengths of pure Mg increased with the addition of GMB particles, with Mg-25 wt % GMB exhibiting the maximum compressive yield strength (CYS) of 161 MPa and an ultimate compressive strength (UCS) of 232 MPa for a GMB addition of 5 wt % in Mg. A maximum failure strain of 37.7% was realized in Mg-25 wt % GMB foam. The addition of GMB particles significantly enhanced the energy absorption by -200% prior to compressive failure for highest filler loading, as compared to pure Mg. Finally, microstructural changes in Mg owing to the presence of hollow GMB particles were elaborately discussed. © 2017 by the authors. Licensee MDPI, Basel, Switzerland.Item 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 Hole Quality Assessment in Drilling of Glass Microballoon/Epoxy Syntactic Foams(Minerals, Metals and Materials Society 184 Thorn Hill Road Warrendale PA 15086, 2018) Ashrith, H.S.; Doddamani, M.; Gaitonde, V.; Gupta, N.Syntactic foams reinforced with glass microballoons are used as alternatives for conventional materials in structural application of aircrafts and automobiles due to their unique properties such as light weight, high compressive strength, and low moisture absorption. Drilling is the most commonly used process of making holes for assembling structural components. In the present investigation, grey relation analysis (GRA) is used to optimize cutting speed, feed, drill diameter, and filler content to minimize cylindricity, circularity error, and damage factor. Experiments based on full factorial design are conducted using a vertical computer numerical control machine and tungsten carbide twist drills. GRA reveals that a combination of lower cutting speed, filler content, and drill diameter produces a good quality hole at optimum intermediate feed in drilling syntactic foams composites. GRA also shows that the drill diameter has a significant effect on the hole quality. Furthermore, damage on the hole exit side is analyzed using a scanning electron microscope. © 2018, The Minerals, Metals & Materials Society.Item Quasi-static compressive response of compression molded glass microballoon/HDPE syntactic foam(Elsevier Ltd, 2018) Jayavardhan, M.L.; Doddamani, M.Quasi-static compressive behavior of different density glass microballoon (GMB) reinforced high density polyethylene (HDPE) syntactic foams are investigated in the present work. Reducing the weight of thermoplastic components has been always a high priority in transportation, aerospace, consumer products and underwater vehicle structures. Despite continued interest in developing lightweight thermoplastic syntactic foams, they have not been studied extensively for quasi-static response with focus on wall thickness and volume fraction variations. Compression molded GMB/HDPE sheets are subjected to 0.001, 0.01 and 0.1 s?1 strain rates. Compressive modulus of foams is higher compared to neat HDPE. Increasing strain rates and decreasing filler content increases yield strength for all the foams investigated compared to neat HDPE. Yield strain and energy absorption of GMB/HDPE foams increases with an increasing strain rate and wall thickness. Specific modulus and strength of GMB/HDPE foams are superior and are comparable to neat HDPE. GMB/HDPE foam achieved high stiffness to weight ratio making them suitable for wide variety of applications. Theoretical model based on differential scheme predicts a good estimate of elastic modulus for all the type of GMB/HDPE foams. Finally, property map is exhibited to present comparative studies with existing literature. © 2018 Elsevier LtdItem Influence of materials and machining parameters on drilling performance of syntactic foams(ASTM International, 2018) Ashrith, H.S.; Doddamani, M.; Gaitonde, V.N.; Gupta, N.The effects of drilling parameters and material properties are investigated on epoxy matrix syntactic foams reinforced with 20, 40, and 60 volume percent glass microballoon. The influences of cutting speed, feed, drill diameter, and filler content on drilling performance are studied based on the full factorial design of experiments using tungsten carbide twist drills. Based on experimental results, machinability aspects within the range of the chosen input parameters are predicted using response surface methodology-based models, which can guide industrial practitioners for choosing the appropriate process parameters. Microscopy is conducted on the drilled specimens to understand crack initiation and propagation mechanisms. The thrust force and specific cutting coefficient of syntactic foam are 40 % lower as compared to those of neat epoxy. The surface roughness of syntactic foams is higher than that of neat epoxy. The micrographs of drill bits show negligible tool wear. These results show the possibility of using syntactic foams in industrial applications in which the drilling of material is required for reasons such as joining using bolts. © © 2018 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959Item Influence of microballoon wall thickness on dynamic mechanical analysis of closed cell foams(Institute of Physics Publishing helen.craven@iop.org, 2019) Doddamani, M.Thermoplastics are most commonly used in industrial and consumer products. The growing interest in making them lightweight is always a priority in industrial practices. Investigations on thermoplastic based closed cell foams wall thickness variations for dynamic mechanical analysis (DMA), and crystallinity are scarce. The present study investigates storage modulus, loss modulus, damping, and % crystallinity as a function of glass microballoon/high-density polyethylene (GMB/HDPE) foam wall thickness and volume fraction variations. Crystallinity percentage variation in HDPE and their foams are analyzed through DSC traces. GMBs are mixed with HDPE in plasticorder, and subsequently, GMB/HDPE composite blend is compression molded. Varying wall thickness (particle density variations) GMB particles across three different volume fractions (20, 40 and 60%) are prepared. Storage modulus, loss modulus, and damping are observed to be increasing with particle wall thickness and volume fraction as compared to HDPE matrix resin. Thick walled GMB particle with the highest GMB content registered enhanced storage modulus compared to thin walled ones at lower temperatures. DMA properties increase with increasing wall thickness. Damping is noted to be less sensitive than the storage and loss modulus. Crystallinity is observed to be decreasing with increasing wall thickness and GMB content. Higher crystalline phase contributes towards DMA properties at lower filler loadings while higher wall thickness plays a vital role at higher filler content. © 2020 IOP Publishing Ltd.Item Effect of wall thickness and cutting parameters on drilling of glass microballoon/epoxy syntactic foam composites(Elsevier Ltd, 2019) Ashrith, H.S.; Doddamani, M.; Gaitonde, V.Effect of glass microballoon (GMB) wall thickness and cutting parameters (cutting speed, feed and drill diameter) on thrust force (Ft), surface roughness (Ra), specific cutting coefficient (Kf), cylindricity (CYL), circularity error (Ce-Exit) and damage factor (Fd-Exit) in drilling of GMB/epoxy syntactic foam is presented. CNC vertical machining centre is utilised for conducting experiments based on full factorial design. Significant process parameters are identified through response surface methodology. Wall thickness significantly affects the Ce-Exit and CYL of the drilled hole. Increasing wall thickness significantly reduces the Ra (30%), CYL (41%) and Ce-Exit (56%) due to the increased thermal stability of syntactic foams. This observation is very crucial for the syntactic foams used in structural applications pertaining to structural stability. Drill diameter is observed to be significant for Ft, Ra, CYL and Fd-Exit; while Kf is governed by feed. Furthermore, grey relation analysis (GRA) is used to identify the specific combination of process parameters to obtain good quality drilled hole. Combination of higher particle wall thickness and feed, lower cutting speed and drill diameter produces a sound hole quality as observed from GRA. Hole quality is highly influenced by drill diameter followed by cutting speed and GMB wall thickness. The present study offers guidelines for the industries (structural applications) to produce quality holes in GMB reinforced epoxy matrix. © 2018 Elsevier LtdItem 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.Item Wear behavior of glass microballoon based closed cell foam(Institute of Physics Publishing helen.craven@iop.org, 2019) Doddamani, M.Present work deals with dry sliding wear response of hollow glass microballoons reinforced lightweight epoxy syntactic (closed cell) foams using a pin on disc apparatus. Influence of glass microballoons content on wear behavior of hollow glass microballoons/epoxy foams in dry sliding mode is investigated. Effects of sliding velocity (1 and 3 m s-1), normal load (30-50 N), sliding distance (1 and 3 km) and glass microballoons content (20, 40 and 60 volume%) are investigated. The rate of wear declines with increasing glass microballoons content and sliding distance. Syntactic foams with perfectly spherical glass microballoons exhibit enhanced resistance to wear as compared to neat resin samples due to better constituents compatibility. Specific wear rate shows noticeably decreasing magnitude with higher applied load. Decrease in frictional coefficient is observed with higher filler loadings. Lowest wear rate of 1.6 mm3 km-1 is noted for sliding velocity and load of 3 m s-1 and 50 N respectively with 60 filler volume %. Low wear values with higher glass microballoon loadings support the feasibility of utilizing such foams in wear-prone applications in weight sensitive structures. Wear mechanisms are studied using scanning electron microscopy. Finally, property map is presented to compare the observed wear results with the existing studies available on dry sliding wear response. © 2019 IOP Publishing Ltd.Item Mechanical behaviour of additively manufactured bioactive glass/high density polyethylene composites(Elsevier Ltd, 2020) Jeyachandran, P.; Bontha, S.; Bodhak, S.; Balla, V.K.; Kundu, B.; Doddamani, M.Bioactive glass (BAG) is a well-known biomaterial that can form a strong bond with hard and soft tissues and can also aid in bone regeneration. In this study, BAG is added to a polymer to induce bioactivity and to realize fused filament fabrication (FFF) based printing of polymer composites for potential orthopaedic implant applications. BAG (5, 10, and 20 wt%) is melt compounded with high density polyethylene (HDPE) and subsequently extruded into feedstock filament for FFF-printing. Tensile tests on developed filaments reveal that they are stiff enough to resist forces exerted during the printing process. Micrography of printed HDPE/BAG reveals perfect diffusion of raster interface indicating proper selection of printing parameters. Micrography of freeze fractured prints shows the homogeneous distribution and good dispersion of filler across the matrix. The tensile, flexural, and compressive modulus of FFF-printed HDPE/BAG parts increases with filler addition. BAG addition to the HDPE matrix enhances flexural and compressive strength. The tensile and flexural behaviour of FFF-prints is comparable to injection molded counterparts. Property maps exhibit the merits of present study over the existing literature pertaining to desired bone properties and polymer composites used in biomedical applications. It is envisioned that the development of HDPE/BAG composites for FFF-printing can lead to possible orthopaedic implants and scaffolds to mimic the bone properties in customised anatomical sites or injuries. © 2020 Elsevier Ltd