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An Investigation of Brittle Fracture of Composite Pressure Vessels with Metal Liner Using a Numerical Approach Based on XFEM

Tavakkoli, Arash | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 44343 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Hosseini Kordkhili, Ali
  7. Abstract:
  8. A metal cylinder tank with composite coating is a pressure vessel which is made of a thin metal layer and a composite layer; like Graphite, and most of the loading is carried by the composite layer. In this study the penny-shaped cracks in cylindrical pressure vessels with composite coating is studied. These kinds of cracks are mostly initiated in manufacturing processes and they have crucial rule in fatigue life and load carrying of the structure. Although there are numerous analytical and numerical methods, they have shortcomings in the case of penny-shaped cracks problems. The strain discontinuity in the interfaces of materials along with discontinuity and singularity due to the crack are among the problems which routine finite element and analytical methods have difficulty to deal with. The extended finite element method along with level set method is applied to these problems in order to overcome the finite element weaknesses. In the XFEM, special enrichment functions are added to the finite element displacement approximation and mesh does not need to conform to the geometry of discontinuities; therefore, a single and regular mesh can be employed for all discontinuities. Therefore, the cost and time of the solution are decrease. The formulation of an axisymmetric finite cylinder with a composite layer containing a penny-shaped crack is performed in a XFEM parametric code in order to evaluate the mode I and II stress intensity factors. The results show that the XFEM decreasing the computational time and cost as well as increasing the accuracy and reliability of the results and also it overcome the FEM weaknesses
  9. Keywords:
  10. Brittle Fracture ; Extended Finite Element Method ; Finite Element Method ; Composite Materials ; Axisymmetric Model

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