Faculty Publications
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Publications by NITK Faculty
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Item Microstructure Characterization and Effective Elastic Properties of Carbon/Carbon Composites(Springer Science and Business Media Deutschland GmbH, 2024) Vishnu, O.S.; Pavan, G.S.In this research, the effective elastic properties of C/C composites are evaluated using FEA-based homogenization technique. The FEA-based homogenization procedure is carried out by generating a Representative Volume Element (RVE). The features in the microstructure are observed with the help of Scanning Electron Microscopy (SEM) images. A detailed study on the SEM images of C/C composites is carried out. The microstructure of C/C composite consists of carbon fibers and carbon matrix. The details obtained from the microstructure are used to generate the RVE of the C/C composite. Random Sequential Adsorption (RSA) algorithm is employed to insert the carbon fibers inside the RVE model. Periodic boundary conditions are imposed on the RVE model, and six different far-field strains are applied on the RVE. For each case of far-field strains, the effective response of the RVE model is evaluated. The effective elastic properties of C/C composites are obtained by combining the volume-averaged stresses of the RVE for each case of far-field strains. The results from the numerical study are compared with those from the Mori–Tanaka method. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.Item Micromechanical Analysis of Carbon/Carbon Composites with Pore Characterization(Springer Science and Business Media Deutschland GmbH, 2025) Vishnu, O.S.; Paul, J.; Pavan, G.S.In this study, the elastic properties of carbon/carbon (C/C) composite are computed by incorporating the presence of pores. Microstructure of C/C composites is analysed using scanning electron microscope (SEM) images. The pores inside the C/C composite are characterized based on area, shape and dimensions. Thirty-six SEM images are analysed. Based on this analysis, a three-dimensional RVE of C/C composite is constructed. The number of pores, their size and spatial distribution in the RVE is given by the analysis. Carbon fibres inside the representative volume element (RVE) are generated using the random sequential adsorption algorithm (RSA). Once the model is generated, periodic boundary conditions are imposed on the RVE model using Python script in Abaqus CAE. Effective elastic properties of C/C composites are computed using the finite element analysis (FEA)-based homogenization method. The effect of pore size distribution on the elastic properties of C/C composite can be understood from this study. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.Item Multiscale numerical modeling of clay brick masonry under compressive loading(Springer Science and Business Media Deutschland GmbH, 2024) Honnalli, S.; Vishnu, O.S.; Pavan, G.S.Masonry is generally comprised of periodic arrangement of masonry unit bonded together with mortar. Masonry is a heterogenous material and exhibits orthotropic behavior. In this study, the elastic-inelastic behavior of brick masonry under compressive loading is predicted using Finite Element Analysis (FEA) based homogenization approach. A three-dimensional repetitive unit cell representing English bond brick masonry is adopted for the homogenization procedure. The proposed approach requires elastic properties, peak compressive and tensile stress, and strain at peak stress values of brick and mortar as the inputs. Material non-linearity in brick and mortar is modeled using concrete damage plasticity model present in ABAQUS software. Using the FEA-based homogenization approach, homogenized stress–strain response of brick masonry subjected to compressive loading (both, normal and parallel to bed joint) and shear loading are obtained. Failure of masonry due to progressive damage development in bricks and mortar joints when subjected to compressive loading is studied. A user-defined material (UMAT) code is developed based on homogenized stress–strain curves. This UMAT can be adopted as constitutive relationship for macro scale modeling of brick masonry using ABAQUS software. The performance of the UMAT is assessed by simulating compression test experiments performed on masonry assemblages found in the literature. The UMAT is found to be satisfactory in predicting the behavior of masonry under compression. © Springer Nature Switzerland AG 2024.