Journal Articles
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Item The effect of the particle shape and strain rate on microstructure and compressive deformation response of pure Ti-foam made using acrowax as space holder(Elsevier Ltd, 2015) Mondal, D.P.; Patel, M.; Jain, H.; Jha, A.K.; Das, S.; Dasgupta, R.Titanium foams of varying amount of porosities have been made using acrowax bits as a space holder through powder metallurgy route. Two types of Ti-particles were used: (i) angular and (ii) spherical in order to see the effect of particle shape on microstructure and deformation behavior. The compressive deformation behavior of Ti-foams with varying porosities and type of particles are studied under different strain rates. It is observed that the microstructural characteristics of Ti-foam varied marginally with the shape of Ti-particles. But the shape of particles influenced reasonably the deformation responses of Ti-foam. The plateau stress, modulus and energy absorption follow power law with relative density irrespective of shape of Ti-particles. All these parameters in Ti-foams are almost invariant to the strain rate. The empirical constants associated with different empirically developed power law relations are different for different shape of Ti-particles. © 2014 Elsevier B.V.Item An experimental investigation on low-velocity impact response of novel jute/rubber flexible bio-composite(Elsevier Ltd, 2019) Mahesh, V.; Joladarashi, S.; Kulkarni, S.M.This paper presents an experimental investigation on low velocity impact (LVI) behaviour of flexible biocomposite laminates with different stacking sequence namely jute/rubber/jute (JRJ), jute/rubber/rubber/jute (JRRJ), jute/rubber/jute/rubber/jute (JRJRJ) and subjected to different impact energy levels using a conical shaped impactor. The performances of the proposed flexible composites are evaluated based on their energy absorption, peak force, coefficient of restitution (CoR), energy loss percentage (ELP) and failure behavior. Results indicated that JRJ provides better energy absorption and JRJRJ provides better damage resistance when subjected to LVI. Microscopic analysis revealed that the flexible composites fail mainly due to the tearing mechanism of the matrix as opposed to cracking in case of conventional stiff composites. It was also found that flexible composites are free from delamination. Compared to conventional stiff composites, there is no catastrophic failure observed in the proposed flexible composite. The overall performance evaluation of these proposed flexible composites indicates that these flexible composites can be potential sacrificial materials such as claddings used to protect primary structural components subjected to LVI. The systematic methodology employed in the present study serves as a benchmark for the effective utilization and selection of flexible composites for LVI applications. © 2019 Elsevier LtdItem Performance study of jute-epoxy composites/sandwiches under normal ballistic impact(China Ordnance Society, 2020) Rajole, S.; Ravishankar, K.S.; Kulkarni, S.M.This study is undertaken to explore the use of natural fiber Jute-epoxy (JE), Jute-epoxy-rubber (JRE) sandwich composite for ballistic energy absorption. Energy absorbed and residual velocities for these composites are evaluated analytically and through Finite Element Analysis (FEA). FE analysis of JE plates is carried out for different thicknesses (3, 5, 10 and 15 mm). JE plates and JRE sandwiches having the same thickness (15 mm) are fabricated and tested to measure residual velocity and energy absorbed. The analytical results are found to agree well with the results of FE analysis with a maximum error of 9%. The study on JE composite plate reveals that thickness influences the energy absorption. Experimental and FE analysis study showed that JRE sandwiches have better energy absorption than JE plates. Energy absorption of a JRE sandwich is about 71% greater than JE plates. Damages obtained from FEA and testing are in good agreement. SEM analysis confirms composites failed by fiber rupture and fragmentation. © 2019 The AuthorsItem Surface gravity wave scattering by multiple energy absorbing structures of variable horizontal porosity(Taylor and Francis Ltd., 2020) Venkateswarlu, V.; Praveen, P.; Karmakar, D.The oblique wave scattering by fully-extended two-layered, three-layered and submerged two-layered porous structures occupying finite width is reported using an analytical model based on the eigenfunction expansion method. The fully extended two-layered structure is composed of two porosities and friction factors in the surface porous layer and the bottom porous layer. In addition, the three-layered energy-absorbing structure is composed of two-porous layers along with the bottom rigid layer to replace the natural seabed variation. Further, the study is extended for multiple energy-absorbing structures to report the impact of free spacing available between the two subsequent structures on fluid resonance. The two-layered porous structure dispersion relation is derived and solved using step approach and Newton-Raphson method. The derived analytical results are validated with the published results of notable authors. The effect of the surface and bottom layers porosity, friction factor, free spacing, structural width, number of structures, and angle of contact on the wave scattering is reported. Finally, the comparative study between the single and multiple energy absorbing structures of multiple horizontal layers is discussed. Further, the significance of the critical angle of contact and fluid resonance for better wave blocking is presented precisely, which is essential for the coastal engineers to design offshore structures. © 2020 Japan Society of Civil Engineers.Item Damage mechanics and energy absorption capabilities of natural fiber reinforced elastomeric based bio composite for sacrificial structural applications(China Ordnance Industry Corporation, 2021) Mahesh, V.; Joladarashi, S.; Kulkarni, S.M.The present study deals with the experimental, finite element (FE) and analytical assessment of low ballistic impact response of proposed flexible ‘green’ composite make use of naturally available jute and rubber as the constituents of the composite with stacking sequences namely jute/rubber/jute (JRJ), jute/rubber/rubber/jute (JRRJ) and jute/rubber/jute/rubber/jute (JRJRJ). Ballistic impact tests were carried out by firing a conical projectile using a gas gun apparatus at lower range of ballistic impact regime. The ballistic impact response of the proposed flexible composites are assesses based on energy absorption and damage mechanism. Results revealed that inclusion of natural rubber aids in better energy absorption and mitigating the failure of the proposed composite. Among the three different stacking sequences of flexible composites considered, JRJRJ provides better ballistic performance compared to its counterparts. The damage study reveals that the main mechanism of failure involved in flexible composites is matrix tearing as opposed to matrix cracking in stiff composites indicating that the proposed flexible composites are free from catastrophic failure. Results obtained from experimental, FE and analytical approach pertaining to energy absorption and damage mechanism agree well with each other. The proposed flexible composites due to their exhibited energy absorption capabilities and damage mechanism are best suited as claddings for structural application subjected to impact with an aim of protecting the main structural component from being failed catastrophically. © 2020 The AuthorsItem Mechanical properties of MWCNTs and graphene nanoparticles modified glass fibre-reinforced polymer nanocomposite(Springer, 2021) Seshaiah, S.; Reddy, K.V.K.; Sahu, R.K.; Katiyar, J.K.In the present study, the multi-walled carbon nanotubes (MWCNTs) and graphene nanoparticles were used as a reinforcement to fabricate glass fibre polymer composite at different orientations (unidirectional glass fibres 0° and 90°; woven glass fibres 0°/90° and 45°/45°). The composites were developed using hand lay-up-assisted vacuum bagging method at 1 torr pressure. The concentrations of nanoparticles (~diameter 5–20 nm) were varied in the range of 0.1–0.3 wt% in the matrix. The mechanical properties like impact strength, tensile strength and fatigue strength were carried out on Izod and Charpy machine, universal testing machine and computer-controlled machine under sinusoidal wave, respectively. It is observed that the glass fibre/epoxy composite blended with MWCNTs/graphene by 0.2 wt% has shown higher fatigue life by 56%, higher tensile strength by 36% and higher capability of energy absorption by 927.7% in notched type and lower capability of energy absorption by 155.43% in un-notched type, as compared to pure composite. The increment in properties is due to the better bonding between fillers and matrix. However, the increase of MWCNTs and graphene nanoparticles by wt% in composite laminates have shown lower fatigue strength because of the agglomeration of MWCNTs particles in matrix that caused the propagation of fatigue cracks under cyclic loading. Further, the damage behaviour of composite materials was analysed using scanning electron microscopy. It is found that a different damage behaviour in each composite is observed which is attributed to the matrix cracking, fibre rupture, fibre pullout, fibre split and fibre de-bonding. © 2021, Indian Academy of Sciences.Item Densification mechanics of polymeric syntactic foams(Elsevier Ltd, 2022) Prabhakar, P.; Feng, H.; P Subramaniyan, S.; Doddamani, M.In this paper, a fundamental understanding of the densification mechanics of polymeric syntactic foams under compressive loading is established. These syntactic foams are closed cell composite foams with thin-walled microballoons dispersed in a matrix (resin) whose closed cell structure provides excellent mechanical properties, like high strength and low density. There are several parameters that can contribute towards their mechanical properties, including, microballoon volume fraction, microballoon wall thickness, bonding between the microballoons and the matrix, and the crushing strength of microballoons. Conducting purely experimental testing by varying these parameters can be very time sensitive and expensive. Also, identification of densification mechanics is challenging using experiments only. Higher densification stress and energy are favorable properties under foam compression or crushing. Hence, the influence of key structural and material parameters associated with syntactic foams that dictate the mechanics of densification is studied here by implementing micromechanics based computational models and multiple linear regression analysis. Specifically, specific densification stresses and energy, which are densification stresses and energy normalized by weight, are evaluated which are more relevant for a wide variety of weight saving applications. Microballoon crushing strength and volume fraction are identified as the parameters that have the higher influence on densification stress and energy, and their specific counterparts, whereas the interfacial bonding has the least impact. In addition, designing aspects of syntactic foams with specified overall density are discussed by mapping microballoon volume fraction and wall thickness. The regression model allows for establishing wall thicknesses and corresponding volume fractions that result in higher densification properties for a specified overall foam density. © 2022 Elsevier LtdItem Influence of basalt fiber on the behavior of beam - column joint under cyclic loading(Elsevier Ltd, 2023) Dineshkumar, G.; Palanisamy, T.Beam-column joints are immensely complicated areas of reinforced concrete constructions. The strengthening of such components can have a significant impact on the earthquake resistant constructions because the rapid collapse of a building could occur if these beam-column joints fail. Recently, designing of reinforced concrete beam-column joints to resist earthquake load becomes more important using ductile design and high strength material. The fibers addition in a concrete directs to an improvement in cracking resistant, ductility, deformation and energy absorption capacity. However, there are currently many distinct types of fibres with various materials and geometric features are used in fiber reinforced concrete to improve the above said properties. The use of basalt fibre, an alternative material made from natural sources that comes from volcanic rock, is the main topic of this essay. The beam-column junction was used to assess the structural behaviour parameters for basalt fibre reinforced concrete, including load–deflection behaviour, ductility, stiffness value, energy absorption capacity, and energy index. From this work, it shows that the natural based basalt fiber shows excellent structural behavior when compared to control concrete. Basalt Fiber Reinforced Concrete (BFRC) has the potential for widespread application in the construction of concrete structures as well as in earthquake-prone regions. © 2023Item Comparative study on low velocity impact behavior of natural hybrid and non hybrid flexible thermoplastic based composites(SAGE Publications Ltd, 2023) Kumbhare, K.; Mahesh, V.; Joladarashi, S.; Kulkarni, S.M.The current study attempts to evaluate the low-velocity impact (LVI) behavior of jute and banana fiber-based hybrid and non hybrid green composites. The proposed composites are fabricated using compression moulding method with variety of positioning of layers namely jute-rubber-jute-rubber-jute (JRJRJ), banana-rubber-banana-rubber-banana (BRBRB), jute-rubber-banana-rubber-jute (JRBRJ) and banana-rubber-jute-rubber-banana (BRJRB). Thus developed composites are subjected to LVI testing using conical and hemispherical shaped impactor in drop weight impact testing machine and different impact velocities of 5 m/s, 10 m/s and 15 m/s. Based on the ability of the proposed composites to absorb energy, coefficient of restitution (CoR), energy loss percentage (ELP), and failure behaviour, the suggested flexible composites’ performances are assessed. The study reveals that JRJRJ composite exhibits better energy absorption capability and BRBRB exhibits least energy absorption capability compared to its counterparts. The damage study reveals that hemispherical impactor leads to more damage area due to its larger contact area whereas, conical impactor results in local penetration. Results reveals that inclusion of jute fiber as reinforcement results in better LVI properties compared to banana fiber. It is also clear that the presence of a compliant matrix improves energy absorption and damage resistance in flexible composites. © The Author(s) 2022.Item Experimental investigation of the in-plane quasi-static mechanical behaviour of additively-manufactured polyethylene terephthalate/organically modified montmorillonite nanoclay composite auxetic structures(SAGE Publications Ltd, 2023) Mahesh, V.; Maladkar, P.G.; Sadaram, G.S.S.; Joseph, A.; Mahesh, V.; Harursampath, D.Apart from the inherent anomalous behaviour under tensile and compressive structures, auxetic structures have shown improved energy absorption characteristics that are of prime interest to various fields of study. This is further exemplified by additive manufacturing (AM) techniques and polymer composites to tailor the shape, geometry and form of these structures. Consequently, this paper aims to characterise the in-plane compressive behaviour and negative Poisson’s ratio (NPR) of the most prominent auxetic structures fabricated additively used polymer nanocomposite materials. The study incorporates the use of glycol-modified polyethylene terephthalate (PETG) and nanocomposites of PETG filled with organically modified montmorillonite (OMMT) nanoclay particles to produce auxetic structures fabricated through fused filament fabrication (FFF). Different structures such as hexagonal re-entrant honeycomb structures, peanut-shaped honeycombs, chiral honeycomb structures and missing rib structures are characterised for their compressive performance through experimental approaches involving mechanical testing and digital image correlation (DIC). Different parameters such as the peak crushing strength, average crushing strength, NPR, specific energy absorption (SEA), and crush force efficiency (CFE) of these structures are evaluated at different strain rates/loading rates for varying concentrations of nanoclay and PETG. It is observed that higher loadings of nanoclay particles lower the compressive strength of the structures. Additionally, the NPR decreases with increasing strain rates and is also influenced by the composition and the resultant stiffness. Moreover, the geometrical parameters of the structure largely influence its strain energy absorption. The results have shown that such material-structure combinations can produce structures of high-performance capabilities suitable for aerospace applications. © The Author(s) 2022.