Dissertation
CHARACTERIZATION OF ADHESIVE AND MODELING OF NONLINEAR STRESS/STRAIN RESPONSE OF BONDED JOINTS
Doctor of Philosophy (PhD), Washington State University
01/2018
Handle:
https://hdl.handle.net/2376/112201
Abstract
Higher strength to weight ratio, better corrosion and fatigue resistance, smoother surface finish, lesser stress and strain concentration than conventional joints are some of the key factors which helped adhesive joints gain attention from industry and research community. Despite these benefits, insufficient understanding in the complex nonlinear stress-strain behavior of adhesives put forth significant challenges in accepting bonded joints for numerous structural applications. When bonded joints are loaded past their yield strength, their deformation is similar, in many respects, to metals undergoing plastic flow. Considering short duration loading scenarios, where time-dependence can be ignored, our preliminary research identified that quantification of yield criterion and hardening rule were the most important factors in modeling adhesive plasticity. The aim of this work was to overcome existing limitations associated with adhesive plasticity and describe the nonlinear stress-strain response of bonded joints with an advanced plasticity model, while comparing a standard and a tough adhesive.
An Arcan fixture was designed to conduct normal-shear mixed-mode tests on bonded joints. Yield stresses were preferred to failure stresses to evaluate the yield criterion. The deviatoric stress-based von Mises criterion was a better representative of adhesive yield surface than the hydrostatic stress-based Drucker-Prager criterion, for both the adhesives.
A shear dominated scarf coupon was used to conduct tension-compression tests and observe adhesive yielding in loading and reverse loading. The tough adhesive was examined to demonstrate kinematic hardening, where yield surface translated without changing its size. However, the standard adhesive demonstrated a combined hardening, where translation (kinematic) component contributed 91% to stress state and expansion (isotropic) component contributed 9%.
Nonlinear kinematic hardening model successfully described the shear stress-strain response for both scarf and lap shear joints, for the tough adhesive. The importance of nonlinear combined hardening was realized significantly for the standard adhesive, where nonlinear kinematic hardening underestimated experimental fail strain by 16% (scarf) and 50% (lap shear), and nonlinear isotropic hardening under predicted experimental fail stress by 24% (scarf) and 12% (lap shear).
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Details
- Title
- CHARACTERIZATION OF ADHESIVE AND MODELING OF NONLINEAR STRESS/STRAIN RESPONSE OF BONDED JOINTS
- Creators
- PREETAM CHANDAN MOHAPATRA
- Contributors
- Lloyd V Smith (Advisor)Vikram Yadama (Committee Member)Jow L Ding (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- School of Mechanical and Materials Engineering
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 126
- Identifiers
- 99900581509601842
- Language
- English
- Resource Type
- Dissertation