Faculty Publications
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Item With a view to study the response to impacts, epoxy-fly ash systems, with filler particles treated with silane material to their surface were fabricated. The test coupons made from the cured thermoset cast slabs were subjected to impact in an instrumented test set up, where, provision existed for recording both load and total energy absorbed with respect to time. The investigation shows that the crack path shift was highest for unreinforced ones, which, display river marks.(Carl Hanser Verlag, Correlating failure features to impact data in epoxy systems without and with silane surface bearing fly ash filler particles in varying amounts; Korrelation von versagensmerkmalen und schlagzähigkeitsdaten in epoxidsystemen mit und ohne silanbeschichtete flugascheteilchen in unterschiedlichen volumenanteilen) Kishore; Ravikumar, N.L.; Kulkarni, S.M.2004Item Epoxy systems with and without different volume fractions of fly ash particulate fillers are made and their absorption due to immersion in saline water maintained at room temperature are established through weight measurements recorded up to 100h. The 100-h exposed samples are additionally subjected to compression tests to evaluate the strength. The results show that both neat epoxy and fly ash-bearing composites exhibit differing levels of aqueous medium absorption - it being less in ash-free samples. When the ash content in the system is large, the absorption levels are high. The data further revealed that the unexposed samples generally record an increasing strength value with ash content. However, for the exposed cases, a reversal in trend with the ash content is noticed. Attempts to explain these differing trends are made in this work by analyzing the features observed on the surface of compression-failed samples using fractography employing scanning electron microscopy (SEM). © 2005 Sage Publications.(Compression strength of saline water-exposed epoxy system containing fly ash particles) Kishore; Barpanda, P.; Kulkarni, S.M.2005Item Behavior of sandwich beams with functionally graded rubber core in three point bending(2011) Doddamani, M.R.; Kulkarni, S.M.; KishoreThe three-point bending behavior of sandwich beams made up of jute epoxy skins and piecewise linear functionally graded (FG) rubber core reinforced with fly ash filler is investigated. This work studies the influence of the parameters such as weight fraction of fly ash, core to thickness ratio, and orientation of jute on specific bending modulus and strength. The load displacement response of the sandwich is traced to evaluate the specific modulus and strength. FG core samples are prepared by using conventional casting technique and sandwich by hand layup. Presence of gradation is quantified experimentally. Results of bending test indicate that specific modulus and strength are primarily governed by filler content and core to sandwich thickness ratio. FG sandwiches with different gradation configurations (uniform, linear, and piecewise linear) are modeled using finite element analysis (ANSYS 5.4) to evaluate specific strength which is subsequently compared with the experimental results and the best gradation configuration is presented. © 2011 Society of Plastics Engineers.Item Influences of dielectric and conductive fillers on dielectric and mechanical properties of solid silicone rubber composites(Springer London, 2019) Manohar Shankar, B.S.; Kulkarni, S.M.Dielectric elastomers are materials being used for electromechanical transduction applications. Their electromechanical response depends on permittivity, Young’s modulus and electric breakdown strength. A factor that limits its application is high operating voltages that can be reduced through improvement in permittivity. One of the methods is by incorporating high permittivity fillers into polymer matrix to obtain dielectric–dielectric composites (DDC).These composites show high permittivity at the cost of reduced flexibility. An alternative solution is development of composites by incorporating organic or inorganic conductive fillers into polymer matrix. These composites show high permittivity with high dielectric loss and low breakdown strength. To overcome both the above limitations both dielectric and conductive fillers are incorporated into dielectric polymer matrix to obtain conductor–dielectric composites (CDC). In this study, high temperature vulcanized solid silicone rubber as matrix has been used to prepare DDC composites with barium titanate (BT) filler and CDC composites with both BT as dielectric and ketjenblack as conductive fillers, using Taguchi design of experiments. The effect of factors such as amount of fillers and curing agent, mixing time in roll mill and curing temperature on the dielectric and mechanical properties are reported. Lichtenecker model predicts the permittivity of the DDC composite more accurately. For the CDC composites permittivity increased by 390%, effective resistivity decreased by 80%, Young’s modulus increased by 368% and Shore A hardness increased by 90% as compared to those of reference matrix. Important interaction effects are observed among both the fillers that are uniformly dispersed without any aggregation. © 2019, Iran Polymer and Petrochemical Institute.Item Processing and investigation of mechanical characteristics on the polydimethylsiloxane/carbon black composites(Institute of Physics Publishing helen.craven@iop.org, 2019) Hiremath, S.; Sangamesh, R.; Kulkarni, S.M.The mechanical adaptability of elastomers has enormous potential in fields such as energy harvesting, micro electro mechanical system (MEMS), sensor, and actuator. A significant issue is to improve the mechanical features of the elastomeric base material by incorporating an appropriate filler. The elastomer Polydimethylsiloxane (PDMS) is reinforced with carbon black (CB) particles that affect mechanical characteristics (Tensile strength, compressive strength, tear strength, etc) and that have a critical impact on the efficiency of the device. The current research examines the mechanical characteristics of plain PDMS with a concentration of CB filler between 5% and 25%. A solution casting method is used to prepare the composite substrate and investigate the impacts of CB loading performance on tensile, compression, tear, and hardness testing. The outcome shows an improvement in mechanical characteristics due to CB material for Young's module as 1.64-3.84 MPa, ultimate tensile strength as 1.86-4.8 MPa, 3.67-4.81 MPa compressive module with the same compressive strength up to 40 percent strain. The tear strength of the PDMS/CB composites is improved by ?111 percent at 25 percent volume fraction of the CB. The composite hardness of PDMS/CB increases by about 30 percent of the plain PDMS material. Continuing with this, Additional mechanical characteristics of PDMS/CB composites on shear and bulk modules are reported. © 2019 IOP Publishing Ltd.Item Influence of conductive and dielectric fillers on the relaxation of solid silicone rubber composites(Institute of Physics Publishing helen.craven@iop.org, 2019) Manohar Shankar, B.S.; Hiremath, S.; Kulkarni, S.M.Flexible dielectrics possessing high permittivity and low loss are desirable for many electromechanical transduction applications. Solid silicone rubber composites are promising materials for electromechanical applications. These composites are fabricated using high-temperature vulcanization process, with various amounts of conductive, dielectric and conductor-dielectric filler and processing parameters. Dielectric and conductivity relaxations of these composites are investigated using dielectric spectroscopy in the 20 Hz-2 MHz frequency range at room temperature. Dielectric relaxations of dielectric filler composites show different behaviour compared to conductive and conductive - dielectric filler composites even with the same filler loading. All composites show increased permittivity at lower frequencies. The maximum permittivity of 46, 5.8 and 46 at 20 Hz was attained for the conductive, dielectric and conductive-dielectric composites respectively at similar filler loadings. The composites follow the AC universality law with exponents in the range of 0.82 to 1.02. The conductive filler is more reinforcing than dielectric filler as seen from the variation of Young's modulus with filler type. Uniform dispersion of fillers is observed for all the three composites. © 2019 IOP Publishing Ltd.Item Effect of ketjenblack and barium titanate on the piezoresistive behaviour of silicone rubber particulate composites(IOP Publishing Ltd, 2021) Manohar Shankar, B.S.; Hiremath, H.; Kulkarni, S.M.In the present study, silicone rubber reinforced with ketjenblack and barium titanate were fabricated using high temperature compression molding method. These particulate composites are characterized for piezoresistive sensitivity. Ketjenblack and barium titanate are the conducting and dielectric fillers in the high temperature vulcanized silicone rubber matrix. The effects of ketjenblack and barium titanate fillers, filler loading, amount of curing agent, curing temperature and mixing time on the piezoresistive properties of these composites were investigated. The piezoresistive sensitivity recorded maximum values of 3.7(10-3) (kPa)-1 for dielectric and dielectric-conductive composites. The linear variation of normalized resistance change was observed for change in pressure up to 20 kPa. The dielectric composite sensitivity increases with reduction in dielectric filler and curing agent loadings, increasing with mixing time and curing temperature. The piezoresistive sensitivity for dielectricconductive composites depends on ketjenblack and barium titanate filler loading. These composites demonstrate interaction effects among the factors. © 2021 The Author(s). Published by IOP Publishing Ltd.Item Experimental studies on mechanical and dielectric behavior of Glycerol filled Silicone rubber composites(IOP Publishing Ltd, 2021) Mathias, K.A.; Hiremath, H.; Kulkarni, S.M.In this study, Silicone rubber composites are prepared with Glycerol filler in three different volume fractions. The samples developed are subjected to mechanical and dielectric testing. The tensile strength increases first and later decreases with Glycerol loading whereas compression strength decreases with Glycerol loading. Modulus of elasticity in tension and compression both decreases with the increase of Glycerol loading. Dielectric permittivity, dissipation factor and conductivity are increases with the increase of Glycerol loading. The Silicone Rubber (SR) composite with 15% volume of Glycerol filler shown a maximum reduction in modulus of elasticity of 29% (in tension) and 16.8% (in compression), and maximum improvement in the dielectric permittivity of 112% compared to neat silicone rubber. The reduction in modulus of elasticity with an increase in dielectric permittivity with an increase in Glycerol loading suggests that this material is a potential candidate for materials to be used in soft dielectric sensors and actuator applications. © 2021 IOP Publishing LtdItem Study on low-frequency dielectric behavior of the carbon black/polymer nanocomposite(Springer, 2021) Hiremath, H.; Mathias, K.A.; Sondar, P.R.; Shrishail, M.H.; Kulkarni, S.M.Recently, polymer-based dielectric materials have become one of the key materials to play an essential role in clean energy production, energy transformation, and energy storage applications. The end usage is the energy storage capability because it is a trade-off between dielectric permittivity, dielectric loss, and dissipation factor. Hence, it is of prime importance to study the dielectric properties of polymer materials by adding filler material at a low-frequency range. In the present study, polydimethylsiloxane/carbon black nanocomposites are prepared using the solution cast method. The dielectric properties, such as dielectric constant, dielectric loss, and dissipation factors due to the concentration of filler particles and low-frequency effect on the nanocomposites, are examined. Also, different empirical models are used to estimate the dielectric permittivity of polymer nanocomposites. The low-frequency range of 100 Hz to 1 MHz and the effect of varying volume fractions of carbon black show a significant change in the dielectric properties. It is found that the nanocomposites have a higher dielectric permittivity than the base polymer material. It is also observed that an increase in filler concentration increases the dielectric permittivity, which is confirmed with an empirical model. © 2021, The Author(s).