Investigation of the Tearing Mechanism of Bonded Soft Elastomers with Finite Interfacial Friction

• Author / Creator

  Lengyel, Tamran H.

• The role of interfacial slippage on the deformation and stress fields near an interfacial crack are investigated in detail. First, the limiting extents of interfacial bonded friction, defined as the frictionless' andno-slip' cases, were modeled as hyperelastic elastostatic boundary value problems in plane strain. Using ideas similar to a fracture mechanics cohesive zone model, the `finite friction' case is established as a shear stress threshold on the bonded surface which if exceeded, allows interfacial slippage. The solutions of all three of these boundary value problems are found in the near field of the crack front using asymptotic analysis. Comparison of these solutions confirm experimental results that the inhibition of interfacial slip in the no-slip case caused material to contract inward producing a non-vertical surface angle that is shown to be a ratio of the in-plane stress components. The finite friction and frictionless cases were found to be related in that they both showed interfacial slippage after loading and the surface angle was perpendicular to the bonded interface. Further, the frictionless case is achieved when the finite friction threshold is set to zero, and in the presence of interfacial friction on the bonded edge there was a reduction in movement and the crack opening profile became more blunted or sharpened depending on the direction of slip. Extensive numerical simulations were performed using commercial finite element analysis software. Simulations for all three friction cases were studied and the results showed strong agreement with the analytical near field findings. Using the numerical data, the effects of far-field loading conditions on the remaining constants in the near-field solutions were quantified and discussed. Through the course of these simulations, it was identified that the direction of loading also plays a significant role on the deformation and stress fields near the crack front. The blunting effect occurred when the loading direction was more perpendicular and the interfacial slip moved to the right. However, when the loading direction was more tangential to the surface away from the crack the deformation field was sharpened and material in the slip-zone moved to the left. This direction of transition was also affected by the total deflection of the far-field loading. Moreover, the amount of blunting was found to be directly related to the magnitude of the stress threshold, and depending on the shear stress direction on the bonded edge (linked to the direction of slippage), produces significantly different normal stress magnitudes and failure modes. From the results presented in this study, a method of quantifying interfacial friction through deflection geometry is introduced and design considerations for desired adhesive tearing mechanisms are provided.

• Subjects / Keywords

  • Interface cracks
  • Asymptotic analysis
  • Interfacial slippage
  • Finite-element-analysis
  • Finite deformation

• Graduation date

  Fall 2015

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3C24QT0X

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.