Faculty Publications

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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.
Experimental and numerical investigation on the elastic properties of luffa–cenosphere-reinforced epoxy hybrid composite
(John Wiley and Sons Inc, 2024) Gurjar, A.K.; Kulkarni, S.M.; Joladarashi, S.; Doddamani, S.
Estimating the elastic characteristics of natural fiber-reinforced polymer composites such as luffa fiber reinforced with epoxy is challenging. The structure of luffa cylindrica is complex, like a three-dimensional natural fibrous mat, netting-like structure. The multiscale modeling of such structures is the challenge to be addressed. The prime objective of this work is to determine the specific elastic properties of luffa–cenosphere-reinforced epoxy (LCE) composite, considering the effect of filler volume fractions. Furthermore, multiscale modeling techniques, such as representative volume elements (RVEs) of finite element techniques with chopped, unidirectional, plain, and twill weaving fiber arrangements, were employed. The longitudinal modulus, transverse modulus, shear modulus, and Poisson's ratio were predicted through these modeling approaches. However, experimental and analytical methodologies, including the rule of mixture and Halpin–Tsai, were considered to validate the finite element analysis results. The elastic characteristics of LCE composite were therefore shown to be enhanced by increasing filler volume fraction. However, the cenosphere's 20% volume fraction has the highest elastic properties as determined by analytical, experimental, and computational models. Analytical and finite element simulation results were compared with the experimental results, and based on the findings, the most suitable (unidirectional, chopped, plain, and twill weaving) RVE was identified for finite element modeling of LCE composite for the evaluation of elastic properties. Results from practical approaches and the RVE twill weaving model showed good agreement, with less than 1% error, compared to the other analytical and finite element methods. Highlights: NFCs are gaining ground in polymer composites. Overcoming challenges in modeling of luffa fiber inside epoxy matrix. The study uses multiscale modeling with diverse fiber arrangements. Experimental and analytical methods used to confirm FEA results. Increased cenosphere volume fraction boosts LCE composite properties. © 2024 Society of Plastics Engineers.
Enhancing tool longevity through TiN coating in multistage cold forging: implementation and analysis using Archard’s wear theory and FEA
(Springer-Verlag Italia s.r.l., 2025) Kulkarni, V.P.; Kulkarni, S.M.; Patil, S.B.; Anshul, A.
Multistage cold forging is widely used in manufacturing; however, high punch wear limits tool life, increasing operational costs and downtime. This study examines the effect of Titanium Nitride (TiN) coating on punch life in multistage cold forging using Archard’s wear theory and Finite Element Analysis (FEA). The research addresses challenges related to tool wear and premature failure, which impact production efficiency, by comparing the punch life of uncoated and TiN-coated punches under identical forging conditions. Archard’s wear theory describes the progressive wear behavior of TiN-coated punches, while FEA simulations with Simufact Forging provide detailed visualizations of stress distributions, wear hotspots, and failure mechanisms. The results show a significant improvement in punch life with TiN-coated punches, where the uncoated punch lasted 9,520 strokes, and the TiN-coated punch lasted 18,051 strokes, representing an increase of approximately 89.6%. Further FEA analysis corroborated these findings, predicting 9,622 strokes for the uncoated punch and 19,496 strokes for the TiN-coated punch.These findings confirm that TiN coatings effectively enhance tool durability, reduce wear, and optimize cold forging processes, thereby reducing operational costs and improving overall efficiency. © The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature 2025.

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