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 Experimental and numerical investigation on low-velocity impact response of sandwich structure with functionally graded core(John Wiley and Sons Inc, 2024) Mohan Kumar, T.S.; Joladarashi, S.; Kulkarni, S.M.; Doddamani, S.The present research investigates optimizing the impact resistance of functionally graded sandwich structures using experimental and numerical approaches. The low-velocity impact (LVI) responses of functionally graded sandwich composite (FGSC) with different configurations with skin material jute/rubber/jute (JRJ) and core material having epoxy and sea sand by volume fraction of sea sand at 0%, 10%, 20%, and 30%. Sandwich structures were impacted with LVI (5.89, 10.92, and 15.18 m/s), with the impactor dropped from heights of 0.5, 1, and 1.5 m with precompressed spring loads. FGSC samples are considered a deformable body, and the impactor is modeled as a rigid body using commercially accessible dynamic explicit software. The burn-out test and weight method were used to test the core's gradience; both methods' results substantially matched, and the variance in gradation could be observed. The proposed sandwich structure characteristics are examined by energy absorption, peak force, energy loss percentage, and coefficient of restitution. Results showed that SC30S provides greater energy absorption and superior damage resistance when tested on LVI. To evaluate the accuracy of experimental findings in predicting the indentation behavior of the sandwich structure, the finite element analysis was used to compare with the experimental results. According to the examination of these proposed FGSC overall performance, they could potentially be employed as sacrificial materials for LVI applications like claddings to shield major structural components. The systematic approach used in this work serves as a standard for choosing and using FGSC effectively for LVI applications. Highlights: Low-velocity impact behavior of sandwich structures was investigated. Combining flexible skin and epoxy core enhances energy absorption. Based on impact energy levels, impact damage areas were determined. Examined sandwich structure advantages in structural and aerospace uses. In terms of time and cost, the numerical analysis method would be useful. © 2023 Society of Plastics Engineers.Item High-Velocity Impact Behavior of Sandwich Composite with Compliant Skin and Sea Sand Strengthened Functionally Graded Core: Experimental and FE Approach(Korean Fiber Society, 2025) Mohan Kumar, T.S.M.; Joladarashi, S.; Kulkarni, S.M.; M, V.The present study investigates optimizing the impact resistance of novel functionally graded sandwich composites using numerical and experimental approaches. The high-velocity impact (HVI) behavior of functionally graded core sandwich composite (FGCSC) with bio-based jute/natural rubber skin and epoxy/sea sand (varying sea sand percentage 0, 10, 20 and 30%, and varying core thickness 10, 20, and 30 mm) functionally graded core. High-velocity impact (HVI) tests are performed using gas gun equipment at an impact velocity ranging from 200, 275, and 350 m/s. The weight residual and burnout method were used to test the gradience of core; both techniques showing significant correlation, and the variance in gradation could be observed. For FE analysis, the FGCSC are represented as deformable bodies, and the bullet is defined as a rigid body using commercially available dynamic explicit software. The HVI test results show that the proposed FGCSC has higher energy absorption capabilities, with core thicknesses of 30 mm and sea sand composition of 30%, resulting in a 1.80% improvement in energy absorption. A finite element study is also carried out to correlate the results, and the obtained results are in better agreement with the experimental findings. The damage analysis indicates that the developed FGCSC with flexible face sheets results in better damage mitigation. The findings suggest that FGCSCs are highly effective for bullet-proofing applications, including personal protective gear and structural components in defense. Further study and optimization could enhance the applicability of these sandwich composites in various protective and structural uses. © The Author(s), under exclusive licence to the Korean Fiber Society 2025.