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Numerical Modeling of Cohesive Crack Growth in Polymers Considering Large Deformations using XFEM

Alavi, Mostafa | 2024

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 57843 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Kazemi, Mohammad Taghi
  7. Abstract:
  8. According to sensitive applications of polymers and polymeric materials, there is a large amount of efforts to understand its behavior in the presence of crack. In this thesis, the influence of nonlinear behavior of the polymers is investigated on the behavior of theory fracture process zone. First, a nonlinear rate-dependent cohesive rule based on a novel incorporation by Schapery nonlinear coefficients is suggested to model crack growth in the case of polyethylene which is well-defined through the Schapery nonlinear constitutive equation. As the matter between the crack faces in a polymeric medium like polyethylene may tolerate large strain ranges during crazing and before complete separation, it may involve stress-dependent factors as same as bulk material. A useful damage-creeping cohesive rule is selected and its creeping part is extended in a way to incorporate the nonlinear Shapery parameters. The augmented relation is fitted to both high and low constraint results and applied to an experimented medium using Extended Finite Element Method (XFEM) to evaluate its ability to properly predict cohesive crack propagation. After that, large deformation framework of XFEM is applied on a de-bonding viscoelastic layer problem to show large deformation assumption essentiality for true prediction of cohesive crack propagation in polymers when they are exposed to high strain ranges. In a further step, the suggested XFEM framework is applied on a mixed-mode problem. The results are in good agreement with the existing experimental outputs. The suggested framework may illuminate a way of expressing the damage zone in polymers using nonlinear specifications of the bulk material
  9. Keywords:
  10. Cohesive Crack ; Extended Finite Element Method ; Polymeric Materials ; Schapery Equation ; Nonlinear Viscoelasticity ; Crack Growth ; Large Deformation

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