Faculty Publications

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Publications by NITK Faculty

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Author: search.filters.author.Gurjar, A.K.

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    Ballistic impact analysis of multilayered armour system using finite element analysis
    (Elsevier, 2024) Doddamani, S.; Kulkarni, S.M.; Joladarashi, S.; Mohan Kumar, T.S.; Gurjar, A.K.
    The application of finite element analysis (FEA) to the ballistic impact analysis of polymer composites used in armor is covered in this chapter. This study aims to assess polymer composite armor materials' performance and establish their resistance to high-velocity projectile impacts. The use of FEA enables accurate simulations of the impact process that take into consideration the properties of the materials, the geometry of the projectile and the armor panel, and the impact conditions. The investigation' findings shed important light on how the polymer composite armor responds to impacts and its capacity to absorb and dissipate impact energy. For the development of cutting-edge armor materials and the multiscale modeling method of armor design, this information is essential. The chapter ends with recommendations for further research as well as a discussion of the difficulties and restrictions of employing FEA for ballistic impact analysis. © 2024 Elsevier Ltd. All rights are reserved including those for text and data mining AI training and similar technologies.
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    Analysis of light weight natural fiber composites against ballistic impact: A review
    (KeAi Publishing Communications Ltd., 2023) Doddamani, S.; Kulkarni, S.M.; Joladarashi, S.; Mohan Kumar, M.K.; Gurjar, A.K.
    The main factors in the ballistic impact mechanism, an incredibly complicated mechanical process, are the target material's thickness, toughness, strength, ductility, density, and projectile parameters. Creating resilient, high-strength, and high-modulus fibers has made it possible to use natural fibers and their composite laminates for various impact-related applications today. Kinetic energy absorption, penetration depth, and residual velocity were the parameters affecting the performance of natural fiber composites used in the armor systems. This review aims to comprehend the several influencing factors that significantly impact the target's ballistic impact performance. In addition to experimental study efforts, many analytical, numerical modeling, and empirical technique-based research approaches have also been considered while analyzing the various components. The paper also examines several factors that determine how well natural fiber composite functions, including internal factors like material composition, characteristics of matrix and reinforcement, the kind and choice of fiber/matrix, failure modes, impact energy absorption, and external factors such as residual velocity, and various projectile nose angles. It also emphasizes the ways to improve composites for high performance and ballistic efficiency, as well as the economic cost analysis of switching out synthetic fibers for natural ones in a ballistic composite. © 2023 The Authors
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    Development of rubber-sand composite for enhanced impact resistance: Implications of vulcanization
    (Elsevier B.V., 2024) Doddamani, S.; Kulkarni, S.M.; Joladarashi, S.; Gurjar, A.K.; Mohan Kumar, T.S.
    Developing rubber-sand composites for enhanced impact resistance faced challenges in material selection, optimisation of vulcanisation, interfacial bonding, and understanding underlying mechanisms. This study provides insights into the effect of vulcanisation on the energy absorption of rubber-sand composites and the potential benefits of adding sand particles as reinforcement, sulfur as a vulcanising agent and carbon black as reinforcement filler. Rubber-sand composites are made from the vulcanisation of natural rubber latex and reinforced with sand particles. Taguchi's design of experiments was used to vary the contents of sulfur (2, 3 and 4) and carbon black (30, 40 and 50) parts per hundred rubber (phr) and sand particles (0, 5 and 10 vol%). After vulcanisation, the composite blocks were prepared using the hot compression moulding technique for experimentation. The shore A hardness and low-velocity drop weight tests have been carried out to investigate the Rubber-sand composite's hardness and energy absorption properties, respectively. The results showed that the increment in the sulfur content increases the hardness of the rubber-sand composite. Additionally, sand particles and carbon black improved the composite's shore A hardness and energy absorption. Multiscale modelling techniques effectively simulated the experimental behaviour of the rubber-sand (Ru-San) composite, with a 3 – 11% error, demonstrating its capability to capture the structural response and damage characteristics under projectile impact conditions. The optimised composite has potential applications in industries that require impact resistance, such as the military, automotive and sports industries. © 2024 Karabuk University
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    Investigation of mechanical properties of luffa fibre reinforced natural rubber composites: Implications of process parameters
    (Elsevier Editora Ltda, 2024) Gurjar, A.K.; Kulkarni, S.M.; Joladarashi, S.; Doddamani, S.
    Natural fiber-reinforced composite materials are highly beneficial due to their excellent strength-to-weight ratio, and the compression molding process is frequently used to prepare natural fiber composites. The primary objective of the present work is to optimize the process parameters of the compression molding method to prepare luffa fiber-reinforced natural rubber composite and investigate the influence of process parameters on mechanical properties. Pre-processing parameters, specifically oven-dry temperature and time, processing parameters such as soaking temperature, time, and compression pressure, and post-processing parameters, such as oven-dry temperature and time, were considered to optimize. Natural rubber in its latex phase is utilized as a matrix material, and luffa fiber is used as reinforcement. The Plackett-Burman screening design technique was employed to identify the impact of different processing parameters on the mechanical properties of the luffa fiber-reinforced natural rubber (LNR) composite, and based on Taguchi's design of experiments, several process parameters were utilized to create L27 orthogonal array and the mentioned composites prepared accordingly. The ASTM standard is followed while testing the composite samples to determine their density, shore A hardness, and tensile strength. The density of the composite is unaffected by the process parameters; however, the shore A hardness of the composite is significantly affected. All the processing parameters most significantly impacted the tensile strength of LNR composites. The optimized process parameters for preparing LNR composite are the pre-oven temperature of 65 °C and time of 150min, the soaking temperature of 75 °C and time of 5min, compression pressure of 1.5 MPa, and the post-oven dry temperature of 55 °C and time of 45min. LNR composite can absorb energy due to its rubber matrix, making it useful for high-impact applications. © 2024 The Authors
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    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.
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    Enhancing energy absorption in rubber–sand (Ru–San) composite blocks against ballistic impact: a multi-objective optimisation approach
    (Springer Science and Business Media B.V., 2024) Doddamani, S.; Kulkarni, S.M.; Joladarashi, S.; Mohan Kumar, T.S.; Gurjar, A.K.
    This study focuses on optimizing process parameters to minimize the thickness of Ru–San composite blocks against high-velocity impact, aiming to enhance projectile energy absorption, particularly in military trench systems. The critical challenge in developing composite blocks as potential sandbag replacements for trench-bunker systems is optimizing their thickness for improved energy absorption during high-velocity impacts. By employing an optimization technique, this study seeks to determine the minimum thickness of the rubber–sand composite block capable of withstanding the full kinetic energy of a projectile without piercing, thereby advancing protective measures in military and security applications. The material used is a rubber–sand composite, consisting of 00 to 20 wt% of sand particles with various sizes ranging from 250 to 750 μm. The optimisation approach employed in this study includes screening design, Vikor and analytic hierarchy process of optimisation techniques. Finite element simulation is used to model the projectile's impact on the rubber–sand composite block and to analyse the energy absorption behaviour of the material under high-velocity impact. The results of this study show that process parameters such as the thickness of the target, wt% of sand, and size of sand particles significantly impact the energy absorption of the rubber–sand composite block. The optimised parameters are determined to be a thickness of 40 mm, 20 wt% of sand, and sand sizes of 750 μm. The findings of this study have important implications for the design and development of materials that can effectively withstand high-velocity impact, particularly in the field of military defence. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2024.
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    Experimental and Numerical Investigation of the Performance of Luffa Fiber-Reinforced Natural Rubber Composites with Process Parameter Optimization using DOE
    (Korean Fiber Society, 2025) Gurjar, A.K.; Kulkarni, S.M.; Joladarashi, S.; Doddamani, S.
    Composite materials have gained significant attention due to their high strength-to-weight ratio and sustainability. In particular, natural fiber-reinforced composites are increasingly investigated as environmentally friendly alternatives to synthetic counterparts. This study focuses on fabricating lightweight and biodegradable luffa fiber-reinforced natural rubber (LNR) composites using compression molding, emphasizing optimizing key processing parameters—temperature, curing time, and compression pressure. Latex-form natural rubber was selected as the matrix owing to its biodegradability, low cost, and compatibility with natural fibers. In contrast, luffa fiber served as reinforcement due to its favorable mechanical properties. The Design of Experiments (DOE) approach, specifically Taguchi’s method, was employed to systematically analyze the influence of processing parameters on physical and mechanical performance. Experimental evaluation of mechanical properties was conducted according to ASTM standards. The rule of mixture was used to evaluate the mechanical properties analytically. The multiscale material modeling finite element (FEM) methods were used to assess the orthotropic properties using the representative volume element technique. Results showed that density was only marginally affected by processing conditions, with ROM and FEM generally overestimating values; however, FEM provided closer agreement to experimental data. Shore A hardness and longitudinal modulus highly depended on curing temperature and time, with optimal properties obtained at 100 °C for 15 min under 1.0 MPa pressure. Similarly, the maximum ultimate tensile strength (0.40 MPa) was achieved under the same conditions, attributed to enhanced fiber–matrix bonding and crosslinking. Statistical analysis (ANOVA) confirmed temperature as the most influential parameter, followed by pressure and curing time. Optimized processing conditions significantly improved fiber–matrix adhesion, resulting in superior mechanical performance. These findings provide reliable processing guidelines for developing high-performance, environmentally sustainable LNR composites, making them suitable for high-impact applications in defense and consumer sectors. © The Author(s), under exclusive licence to the Korean Fiber Society 2025.