Micromechanics Modeling of Advanced Self-Healing Materials

  • Ammar A., Alsheghri

Student thesis: Master's Thesis

Abstract

Self-healing polymers have attracted intensive research interests during the last two decades for being high-potential sustainable materials for civil, military and aerospace applications. Understanding the self-healing mechanisms is of great potential for providing safer, cheaper and more sustainable materials. Crack healing reverses the cracking process and recovers partially or completely the material properties. The focus of this thesis is on modeling polymeric materials with intrinsic cross-linking selfhealing mechanisms. Several attempts were made to model the prescribed self-healing mechanisms using the continuum damage/healing mechanics theory by treating healing as a reduction of the damage density regardless of the nature of crack propagation or healing mechanism. To better understand the self-healing phenomena, there is a need to model the time-and-temperature- dependent intrinsic self-healing mechanism at the micro scale and demonstrate crack initiation, propagation, closure and healing. A phenomenological cohesive zone damage-healing model (CZDHM) for self-healing materials is developed for the first time based on the principle of virtual power and the laws of thermodynamics. The well-known nominal, healing and effective configurations of classical continuum damage-healing mechanics are extended to represent cohesive zone configurations in self-healing materials. A new physicallybased internal crack healing state variable is proposed for describing healing evolution within the crack cohesive zone. A thermodynamics framework for constitutive modeling of time-dependent damage and healing of cracks is used to derive the evolution equation for the prescribed healing variable. The effects of temperature, pressure, resting time, history of healing and damage, and level of damage on the healing behavior of the material are incorporated in the model. Numerical examples are conducted to show the various novel features of the formulated CZDHM.
Date of AwardMay 2015
Original languageAmerican English
SupervisorRashid Abu Al Rub (Supervisor)

Keywords

  • Self-Healing Polymers
  • Sustainable Materials
  • Self-Healing Mechanisms
  • Crack Healing
  • Cohesive Zone Damage-Healing Model
  • Laws of Thermodynamics.

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