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X-WR-CALDESC:Events for Department of Aerospace Engineering
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TZID:Asia/Kolkata
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DTSTART:20260101T000000
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260525T160000
DTEND;TZID=Asia/Kolkata:20260525T170000
DTSTAMP:20260709T075916
CREATED:20260525T043027Z
LAST-MODIFIED:20260525T094140Z
UID:10000129-1779724800-1779728400@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg) :VAM-Based Elastic and Thermo-elastic Micromechanics Models for Homogenization and a VAM2 Multi-scale Model for Composite Beam-Like Structures.
DESCRIPTION:In diverse domains of engineering and high-performance applications\, the use of Fiber-Reinforced Polymer Matrix Composites (FRPMCs) and Metal Matrix Composites (MMCs) has experienced rapid and sustained growth. This trend is primarily attributable to their high specific stiffness\, elevated strength-to-weight ratio\, low Coefficients of Thermal Expansion (CTE)\, and inherently lightweight characteristics\, coupled with the ability to tailor their properties to meet specific design requirements. The effective utilization of such advanced materials necessitates a comprehensive understanding of their structural response\, both at the global and constituent levels. In particular\, precise knowledge of homogenized material properties\, CTEs\, and spatially resolved local fields within the reinforcement and matrix phases is indispensable for predicting structural behavior\, conducting performance assessments\, and achieving optimal designs suited to demanding engineering applications. The growing demand for accelerated yet accurate design cycles further underscores the need for computationally efficient\, yet physically rigorous\, predictive models. \nConventional micro-mechanics and multi-scale modeling techniques are frequently constrained by restrictive kinematic assumptions\, such as pre-specified displacement or stress fields\, whose validity is not inherently guaranteed by the governing equations of three-dimensional elasticity\, and often employ oversimplified treatments of interface continuity conditions. Numerical approaches\, while flexible\, typically rely on computationally intensive discretization and may not rigorously satisfy all interface continuity requirements. These limitations collectively compromise the generality\, accuracy\, and physical fidelity of predicted material and structural responses. \nTo address these shortcomings\, this doctoral research develops a unified\, analytically rigorous\, and asymptotically consistent multi-scale modeling framework for the accurate prediction of homogenized elastic properties\, CTEs\, and fully three-dimensional local field distributions within the constituents of composite materials\, with particular emphasis on beam-like structural configurations. The first segment of the thesis introduces an asymptotically correct micromechanics formulation that eliminates arbitrary field assumptions\, deriving its governing equations directly from the stationary conditions of the total strain energy functional expressed in generalized strain measures. The Variational Asymptotic Method (VAM) is adopted as the mathematical foundation\, while the Hashin–Rosen Composite Cylinder Model (CCM) serves as the physical idealization for the composite Representative Unit Cell (RUC). This approach enables the derivation of closed-form expressions for homogenized elastic properties\, including elastic moduli\, shear moduli\, and Poisson’s ratios\, while rigorously enforcing displacement continuity and transverse stress equilibrium at the reinforcement–matrix interface. The resulting expressions are explicit functions of constituent material properties\, volume fractions\, and geometric parameters. \nThe formulation is subsequently extended to the thermo-elastic regime\, wherein the governing relations are derived from the stationary conditions of the Helmholtz free energy functional\, expressed in generalized strain measures and CTEs. This extension yields closed-form expressions for the effective longitudinal and transverse coefficients of thermal expansion. The predicted elastic moduli and CTEs are extensively validated against existing micro-mechanical solutions\, experimental results\, and literature data for a wide range of composite systems. \nBuilding upon this foundation\, the research advances a VAM2-based multi-scale analytical methodology in which the generalized micromechanics formulation is seamlessly integrated with a macro-scale structural model\, free from restrictive kinematic simplifications. The macro-scale solution prescribes traction boundary conditions to the micro-scale problem in a manner consistent with three-dimensional equilibrium\, while the micro-scale formulation rigorously enforces interface elasticity constraints. This enables the derivation of closed-form expressions for fully three-dimensional local displacement\, strain\, and stress fields in both reinforcement and matrix phases\, parameterized by one-dimensional strain measures\, curvature terms\, constituent properties\, and spatial coordinates. \nThe proposed multi-scale framework achieves computational accuracy comparable to concurrent multi-scale approaches\, while preserving the computational efficiency characteristic of hierarchical methods. Its predictive capability is validated through high-fidelity three-dimensional finite element simulations for arbitrary RUC locations on the beam cross-section\, under simultaneously applied multi-load conditions. \nOverall\, this research establishes a generalizable\, physically consistent\, analytically tractable\, and computationally efficient paradigm for predicting homogenized elastic properties\, CTEs\, and performing multi-scale structural analysis of composite materials. It represents a substantive advancement over prevailing micro-mechanical and multi-scale modeling strategies\, combining theoretical rigor with practical utility for the design and analysis of advanced composite structures. \nThis MS Teams Meeting Link is just for those unable to join pīrēśvarā\, Dr MVVS mūrti & me in-person@CVH Conference Hall\, IISc: AE PhD Colloquium: VAM2 Multiscale Model for Composite Beams & VAM-based Thermoelastic MicroMechanic Homogenization | Meeting-Join | Microsoft Teams : https://teams.microsoft.com/meet/45114276357578?p=KPgojv0HqsJhQKrSzd \n  \nSpeaker: śrī M. V. PEERESWARA RAO \nResearch Supervisors: Dineshkumar Harursampath & Dr MVVS Murthy\, Division Head\, Spacecraft Systems Engg. Group\, URSC\, ISRO
URL:https://aero.iisc.ac.in/event/ph-d-engg-vam-based-elastic-and-thermo-elastic-micromechanics-models-for-homogenization-and-a-vam2-multi-scale-model-for-composite-beam-like-structures/
LOCATION:Conference Hall\, 1st Floor\, CVH\, IISc
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/05/PEERESWARA.jpg
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BEGIN:VEVENT
DTSTART;TZID=Asia/Kolkata:20260518T040000
DTEND;TZID=Asia/Kolkata:20260518T170000
DTSTAMP:20260709T075916
CREATED:20260514T081933Z
LAST-MODIFIED:20260519T082153Z
UID:10000124-1779076800-1779123600@aero.iisc.ac.in
SUMMARY:Ph.D. (Engg) : Mechanical Characterization and Non-linear Analysis of Woven Hyperelastic Composite Laminate using Variational Asymptotic Method.
DESCRIPTION:The increasing demand for lightweight\, multifunctional structures in aerospace and civil engineering applications has driven significant interest in hyperelastic composite laminates. These materials\, capable of undergoing large deformations while maintaining structural integrity\, are particularly suited for deployable space structures\, high altitude airships\, inflatable antennas\, and tensile fabric architectures. However\, accurate prediction of their mechanical behavior requires rigorous constitutive modeling coupled with mathematically consistent dimensional-reduction techniques that make no ad hoc assumptions.\n\nThis thesis presents a comprehensive investigation into the constitutive modeling and asymptotic analysis of hyperelastic composite laminates for high-altitude airship and other inflatable structure applications. Through an extensive literature survey\, Kapton HN® and Nomex® were identified as promising candidate materials for multifunctional membrane structures due to their desirable properties\, including UV resistance\, thermal stability\, helium retention capability\, and mechanical strength. A composite laminate was fabricated using the vacuum bagging technique with Nomex® sandwiched between Kapton HN® layers on the top and bottom\, employing the hand lay-up technique with aerospace-grade epoxy.\n\nAll three constituent materials—Kapton HN®\, Nomex®\, and the fabricated composite laminate—were mechanically characterized through uniaxial tensile tests conducted until failure. The anisotropic nature of Nomex® was further investigated by evaluating micro-fiber angles using image processing of Scanning Electron Microscope (SEM) images taken at 1770× resolution. Incompressible hyperelastic material models were proposed to fit the experimental data for these materials\, subject to constraints from continuum mechanics and the Baker-Eriksen inequalities.\n\nThe isotropic Kapton HN® was accurately represented by the incompressible vYeoh model\, while Nomex® required a modified version of the Holzapfel-Gasser-Ogden (HGO) model to capture its fiber-reinforced characteristics. Notably\, the modified HGO model could estimate fiber angles using an error-optimization algorithm\, and these estimates were validated against fiber angles measured directly from SEM image analysis.\n\nFor the composite laminate\, a superposition-of-energies approach—referred to in the literature as the Rule of Mixtures model—was proposed and mechanically characterized in both longitudinal and transverse directions. The model demonstrated excellent agreement with experimental observations.\n\nBuilding upon the constitutive characterization\, the three material systems were modeled within a geometrically exact kinematic framework for plates. Using the Variational Asymptotic Method (VAM)\, dimensionally reduced\, asymptotically correct models were derived for each material up to first order. This mathematically rigorous approach makes no ad hoc assumptions and systematically accounts for the small parameters inherent in thin structures. The warping functions\, which capture the through-thickness deformation patterns\, were systematically solved as intermediate results for all three materials up to zeroth and first order. The two-dimensional nonlinear constitutive laws were evaluated\, and the mechanical coupling responses were clearly elucidated.\n\nFinally\, a nonlinear finite element analysis was performed to model plates fabricated from these materials under various loading conditions. The VAM-based models were successfully validated against experimental data\, demonstrating the accuracy and predictive capability of the asymptotically derived constitutive laws. This work establishes a rigorous framework for analyzing hyperelastic composite laminates and provides valuable insights for the design of next-generation membrane structures for aerospace and civil engineering applications.\n\nSpeaker: Shaikbepari Mohmmed Khajamoinuddin\n\nResearch Supervisors: Dineshkumar Harursampath  & MR Bhat
URL:https://aero.iisc.ac.in/event/ph-d-engg-mechanical-characterization-and-non-linear-analysis-of-woven-hyperelastic-composite-laminate-using-variational-asymptotic-method/
LOCATION:Conference Hall\, 1st Floor\, CVH\, IISc
ATTACH;FMTTYPE=image/jpeg:https://aero.iisc.ac.in/wp-content/uploads/2026/05/Shaikbepar.jpg
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