Constitutive Modeling and Numerical Investigation of Damage and Healing Phenomena in Self-healing Polymers at Finite Deformation

Shahsavari, Hamid | 2015

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 48770 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Naghdababdi, Reza; Sohrabpour, Saeed
  7. Abstract:
  8. In this thesis, employing the definition of an effective configuration in the Continuum Damage-Healing Mechanics (CDHM), mechanical responses of elf-healing materials are investigated. Firstly, a constitutive model is proposed to investigate damage and healing phenomena in concrete materials. In order to consider the different behavior of concretes in tension and compression, a spectral decomposition of the stress is utilized. In addition, employing the Clausius-Duhem inequality and considering the irreversible thermodynamics, conjugate forces of the damage and healing are expressed. The Gibbs potential energy is decomposed into three parts; elastic, damage and healing. In the next section, we present a phenomenological viscoelastic-viscoplastic-viscodamage-viscohealing constitutive model, developed within the framework of irreversible thermodynamics. The formulation is based on the additive decomposition of the total strain into elastic, viscoelastic and viscoplastic parts in the effective configuration. Thus, the Helmholtz energy is partitioned into elastic, elastic-viscoelastic and viscoplastic parts. Then, each one is divided into deviatoric and volumetric energies. Considering the Clausius-Duhem inequality and Drucker-Prager potential function, the effective stress and effective viscoelastic and viscoplastic strain evolution equations are achieved. Finally, employing the Hencky strain, viscoelastic-viscoplastic response of self-healing materials is investigated at finite deformation. Considering the irreversible thermodynamics and using the effective configuration in the CDHM, a phenomenological finite strain viscoelastic-viscoplastic constitutive model is presented. Considering finite viscoelastic and viscoplastic deformations, total deformation gradient is multiplicatively decomposed into viscoelastic and viscoplastic parts. In this regard, defining the damage and healing variables and employing the strain equivalence hypothesis, the strain tensor is determined in the effective configuration. Satisfying the Clausius-Duhem inequality, the evolution equations are introduced for the viscoelastic and viscoplastic strains. The damage and healing variables also evolve according to two different prescribed functions. Capability of the proposed models in this thesis demonstrated comparing the model predictions in the creep-recovery and repeated creep-recovery with the experimental results available in the literature and a good agreement between predicted and test results is revealed
  9. Keywords:
  10. Constitutive Modeling ; Evolution ; Damage ; Viscoplasticity ; Viscoelasticity ; Large Deformation ; Retrofiting

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