Title page for ETD etd-01212003-110239


Type of Document Master's Thesis
Author Mount, Kristopher Patrick
Author's Email Address kmount@vt.edu
URN etd-01212003-110239
Title Finite Element Analysis of Probe Induced Delamination of a Thin Film at an Edge Interface
Degree Master of Science
Department Mechanical Engineering
Advisory Committee
Advisor Name Title
West, Robert L. Jr. Committee Chair
Dillard, David A. Committee Member
Wan, Kai-tak Committee Member
Keywords
  • half-blister
  • adhesive blister test
  • finite elements
  • energy release rates
Date of Defense 2002-12-19
Availability unrestricted
Abstract
Energy release rates are extracted from non-linear finite element analyses of a thin film bonded to a rigid substrate that is shaft-loaded at its free edge. This geometry is of interest because it simulates a probe test that has proven to be useful in characterizing the adhesion of thin, microelectronic coatings bonded to silicon wafers. Preliminary experimental results indicate that out-of-plane rather than in-plane loading dominates failure in the system. This work therefore focuses on out-of-plane film loading. To validate finite element and energy release rate methodologies, energy release rates from finite element analyses of pressurized and shaft-loaded blister tests are first correlated to theoretical limit cases. Upon validation, mode I, mode II, and mode III energy release rates are extracted from three-dimensional continuum finite element models of the edge-loaded thin film by a three-dimensional modified crack closure method. Having assumed a circular debond as observed experimentally, energy release rates are determined by a step-wise approach around the circumference. The progression of debond is simulated in multiple analyses by altering the boundary conditions associated with increasing the debond radius. Mechanical loading is supplemented with thermal loading, introducing residual stresses in the non-linear analyses. A sensitivity analysis of energy release rates to residual stress is performed. The results indicate that inclusion of residual stress has an important role in both the magnitude and mode-mixity of energy release rates in the thin film. Increasing the length of debond effectively transitions the film from a shearing mode to a bending mode, thereby significantly impacting each mode of energy release rate differently.
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