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Title:A variational framework for multi-scale defect modeling in strained electronics and processing of composite materials
Author(s):Al-naseem, Ahmad
Director of Research:Masud, Arif
Doctoral Committee Chair(s):Masud, Arif
Doctoral Committee Member(s):Duarte, Armando; Lopez-Pamies, Oscar; Garcia, Marcelo H
Department / Program:Civil & Environmental Eng
Discipline:Civil Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):Finite Elements
VMS
Multi-scale
Compressible-Incompressible
B-splines
Electronic Structures
Discontinuity Capturing
Enrichment
Abstract:With the recent advances in material processing technologies and the introduction of the material genome initiative, material processing has gained an increased level of attention in the research community. Primary challenges in most material processing technologies and specifically in composite materials are the uncertainties concerning the material’s performance under loading whether it be static, dynamic or cyclic. That is due to the variabilities in these technologies that may lead to the formation of defects within the material parts at critical location during processing. This dissertation presents a deterministic defect modeling framework based on a system of variationally consistent formulations that allow for the modeling of the material processing stage and incorporate multi-physics coupling for multi-constituent materials. A stabilized and novel discontinuity capturing formulation is developed to model multi-phase flow of the materials and their defect while sharply capturing the jumps in material properties, material compressibility and kinetic reaction across the multi-phase interfaces. The method is based on employing structured non-moving meshes to solve the Navier-Stokes equations employing a finite element method (FEM) stabilized via the Variational Multiscale Method (VMS). Within VMS framework a discontinuity capturing method is derived that allows for sharp discontinuity capturing of the physical discontinuities of across phases within a single numerical element allowing for highly accurate and discrete representation of the interfacial physical phenomena. In addition, surface tension is incorporated into the formulation to discretely model jumps in the pressure field. The multi-phase interface is evolved employing a stabilized level-set method allowing for intricate motion of the two phases and the discontinuities within the Eulerian mesh. The formulation is then expanded to incorporate discontinuities in the governing system of equations allowing for modeling adjacent compressible-incompressible fluids within a unified formulation. Coupled with the thermal evolution within the constituents of the material and accounting for phase change and mass leading to mass transfer across the interface the materials, kinetic evolution of the material viscosities is modeled at the material points accounting for variability in the flow behavior as a function of kinetic curing. Finally, a previously developed isogeometric FEM method is expanded to model quantum defect evolution of strained electronics and the effect of straining on the electronic properties of these materials. Representative numerical tests involving complex multi-phase flows of physical instabilities, hydrodynamic collapse of bubbles and convective mass transfer along with electronic band-gap structures with strain effects are presented as validations and applications for the framework’s robustness. Finally, the chemo-thermo-mechanical coupling and real-life application is presented via a fully coupled problem involving processing of a composite bracket during the early curing stages.
Issue Date:2018-12-07
Type:Thesis
URI:http://hdl.handle.net/2142/102944
Rights Information:Copyright 2018 Ahmad Al-Naseem
Date Available in IDEALS:2019-02-08
Date Deposited:2018-12


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