Thesis
A time dependent nonlinear model of bulk adhesive under static and cyclic stress
Washington State University
Master of Science (MS), Washington State University
2016
Handle:
https://hdl.handle.net/2376/100917
Abstract
Joining components with adhesives has many benefits in engineering design but the complicated mechanical response of them must be understood for certification. The unique time dependent behavior of epoxy resins is important to characterize to understand the long term performance and operating lifetime of adhesive joints. This research studied the response of a standard and toughened adhesive to static and cycled loading compared with linear and nonlinear viscoelastic models. Static load creep tests were done at three stress levels which showed both adhesives behaved nonlinearly. A linear viscoelastic model with a power law compliance was fit to each test and the power law coefficients were then the inputs to a nonlinear viscoelastic model which showed excellent agreement with experiments. There was particular concern for the response during cycled loading where strain can progressively accumulated as cycles increase, known as ratcheting. Both adhesives showed this response however the amount was smaller than expected, a 7.1% increase for standard adhesive and 12.2% for toughened adhesive after 1,000 cycles at 80% of the ultimate tensile strength. In comparison the creep tests after 1,000 seconds at 80% of the ultimate tensile strength showed an increase in strain of 15.9% for standard adhesive and 37.5% for the toughened adhesive. This meant that longer durations at high stress increased strain more than cycled loading. A nonlinear viscoelastic model was derived for cycled loading which showed good agreement at low stress while over predicted strain at high stress by 3.1% for the standard adhesive and 10.8% for the toughened adhesive. There were numerous sources of experimental error, but this was likely a result of the model's sensitivity to the three power law coefficients which showed large variation between coupons.
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Details
- Title
- A time dependent nonlinear model of bulk adhesive under static and cyclic stress
- Creators
- David Andrew Lemme
- Contributors
- Lloyd V. Smith (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Mechanical and Materials Engineering, School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525035901842
- Language
- English
- Resource Type
- Thesis