Faculty Publications
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Publications by NITK Faculty
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Item 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 Instrumented ballistic performance of jute/epoxy sandwich with functionally graded rubber core(Inderscience Publishers, 2012) Doddamani, M.R.; Kulkarni, S.M.The qualitative analysis of instrumented ballistic impact for jute-epoxy sandwiches with fly ash reinforced functionally graded (FG) flexible, compliant rubber core is presented. An attempt is made to study the influence of fly ash weight fraction, jute orientation and core to total thickness (C/H) of sandwich on ballistic performance. Experiments are designed based upon L9 orthogonal array. Analysis of variance (ANOVA) is performed on recorded data to investigate the influence of parameters on ballistic response. An optimal parameter combination is determined leading to higher energy absorption and lower energy required for skin pullout by the bullet. A correlation derived from the results of Taguchi experimental design is proposed as a predictive equation for estimation of energy absorption of sandwiches. Furthermore, for arresting bullet optimum stack thickness of sandwich configuration is presented. Finally, the potential benefits for using such materials as a replacement for sand bags in guarding posts is highlighted. Copyright © 2012 Inderscience Enterprises Ltd.Item Response of fly ash-reinforced functionally graded rubber composites subjected to mechanical loading(2012) Doddamani, M.R.; Kulkarni, S.M.A novel approach to estimate the Young's modulus of a functionally graded rubber composite (FGRC) from the damping ratio is demonstrated with the examples of unreinforced and fly ash-reinforced materials. FGRC coupons were prepared using the conventional casting technique. The occurrence of gradation in the specimens was attributed to the variable density of particles present in the fly ash, settling at different depths. The technique of free vibrations was used for experimentation. The damping response of the FGRC specimens was studied. The results obtained from the experiments showed that, with growing filler weight fraction, the Young's modulus of the composite increased. The empirical model developed to predict the magnitude of the modulus turned out to be in good agreement with experimental data. © 2012 Springer Science+Business Media, Inc.Item Compressive properties of sandwiches with functionally graded rubber core and jute-epoxy skins(2013) Doddamani, M.R.; Kulkarni, S.The compressive behaviour of a new class of sandwich composite made up of jute fiber reinforced epoxy skins and piece-wise linear fly ash reinforced functionally graded (FG) rubber core is investigated in flat-wise mode. FG samples are prepared using conventional casting techniéue. Presence of gradation is éuantified physically by weight method. This paper addresses the effect of weight fraction of fly ash, core to thickness ratio (C/H) and orientation of jute on specific compressive modulus and strength. In each trial five replicates are tested with lower amount of fly ash below the upper skin of sandwich (rubber-up). Results of experimentation are subjected to statistical analysis of variance (ANOVA) to find the influential factor governing the compressive behaviour. Furthermore piece-wise linear gradation is modeled in finite element and strength values are compared with experimental results. Sandwich sample with fly ash content of 40%, C/H of 0.4 and orientations of 30?/60? registered better performance. Specific strength is observed to increase upto 30% filler content followed by stabilization. Finite element results for strength match very well with experimental ones.