Faculty Publications
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Item Understanding Solidification Behavior of Salt Phase Change Material with Added Carbon Nanoparticles Using Computer-Aided Cooling Curve Analysis(Springer, 2022) R, S.; K.n, P.In recent years, nanoparticle-dispersed salt-based phase change materials (PCMs) have emerged to be suitable for thermal energy storage applications. In this work, the carbon nanostructures of graphite, multiwall carbon nanotube (MWCNT) and graphene were separately dispersed in potassium nitrate. Solidification of these nanosalt-PCMs was analyzed using a computer-aided cooling curve analysis technique. The technique is much more effective in comparison with other alternatives such as differential scanning calorimetry, as it is simple and low cost and employs large sample sizes. In the present study, PCM sample size of 1kg was fixed with nanoparticle concentration varying from 0.1 to 0.5% by weight of the sample. The solidification time of the PCM was observed to decrease significantly on addition of nanoparticles indicating an enhancement in the heat removal rate. It is beneficial as the same amount of stored thermal energy can then be withdrawn at a much higher rate. Graphite and MWCNT additions decreased the thermal diffusivity property of the base PCM, while the graphene additions resulted in higher thermal diffusivity. However, the benefits of addition of nanoparticles to the salt-PCM reduced on thermal cycling. SEM images show that the deterioration in the observed enhancements occurred due to agglomeration of nanoparticles. This was observed in the initial 3-4 thermal cycles, and the nanosalt-PCM remained stable thereafter. The PCM developed here offers higher heat transfer rates with superior energy density. © 2021, ASM International.Item Numerical studies on modeling heterogeneity in elastic properties of 8HS woven C/C composites(Taylor and Francis Ltd., 2025) Vishnu, O.S.; Pavan, G.S.; R, S.; Thomas, A.The variation in fiber volume fraction and pores developed at the microscale during the manufacturing process is a source of heterogeneity in the elastic properties of woven Carbon/Carbon (C/C) composites. This study investigates the effect of heterogeneity on the elastic properties of Eight Harness Satin (8HS) woven C/C composites using a two-scale (micro–meso) finite element (FE) homogenization method. At the microscale, variations in fiber volume fraction and porosity are incorporated by generating 25 representative volume elements(RVEs) from the reconstructed CT scan images. The RVEs preserve the shape, size, orientation, and spatial distribution of pores that are present in the microstructure. The carbon fibers are virtually generated inside the 25 micro-RVEs using the random sequential adsorption (RSA) algorithm in accordance with the reconstructed microstructure of actual pores. At the mesoscale, the model incorporates warp and weft yarns embedded in a pyrolytic carbon matrix. Yarn heterogeneity is modeled by subdividing the meso RVE into smaller domains, each assigned elastic properties derived from the microscale RVEs. The degree of heterogeneity was varied using different combinations of the microscale RVEs to assign material properties. This approach effectively incorporates the randomness of the microstructure into the computation of the effective elastic properties of woven composites. The on and off-axis elastic properties of 8HS woven C/C composites are computed, and the results determined from the numerical study are compared with experimental tests conducted on 0° and 45° specimens. This study highlights the importance of fiber volume fraction and pores on material heterogeneity in accurately computing the elastic properties of 8HS woven C/C composites. © 2025 Taylor & Francis Group, LLC.