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Micro-Mechanical Analysis of Matrix Shear Deformation Effect on Energy Release Rate of Fiber/Matrix Interface Debond in Unidirectional Fiber-Reinforced Plastic Composites

Bazargani, Mahsa | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52617 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Hosseini Kordkheili, Ali
  7. Abstract:
  8. The present thesis deals with the effect of matrix shear deformation on energy released due to debonding at fiber/matrix interface during fiber pull out test, which is modeled using two concentric cylinders representing fiber and matrix. Tensile on fiber causes a shear stress at the interface. When this stress exceeds the tensile strength of the interface, debonding occurs at the interface and grows as a crack along the interface. This debonding causes a relative axial displacement between fiber and matrix along the debonded interface, which varies along the debond crack. How fiber/matrix relative displacement changes along the debond region is not known. Thus, the fiber/matrix interface is studied, assuming linear and nonlinear functions for fiber/matrix relative displacement at the debonded interface. Stresses ahead of the crack tip are assumed to be constant and are due to the residual stresses. Stresses in the wake of the crack tip including fiber/matrix axial stresses and matrix shear stress are achieved by considering force balance at the downstream of the crack and applying the boundary conditions at this region. Further, using the maximum shear stress criterion, the initial debond stress is computed. Next, fiber radial stresse along the crack length is considered and using the coulomb friction law, the debond stress is obtained as a function of the debond length. Then, the fracture energy will be computable. Finally, the results of the linear and nonlinear displacement functions are compared and it will be seen that at relatively large ratios of matrix/fiber radius, the difference between the two solutions is quite small. However, when this ratio is small, the difference of the two solutions is not negligible. One of the characteristics of the present analysis is taking the debond length as the only input of the problem, which omits the need for conducting challenging tests and numerical analysis for interface studying of fiber reinforced composites
  9. Keywords:
  10. Micromechanics ; Shear Deformation ; Interfaces ; Unidirectional Composites ; Fibers ; Crack ; Debond Energy

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