Thesis
Effect of cyclic shear loading on thin bonded adhesives
Washington State University
Master of Science (MS), Washington State University
08/2020
DOI:
https://doi.org/10.7273/000004146
Handle:
https://hdl.handle.net/2376/124785
Abstract
Adhesive bonding offers many advantages over other types of fasteners, but much of their behavior is still unknown, which limits their applications. One area of concern is how adhesive bonds respond to cyclic loading. Cyclic loading can cause plastic and viscoelastic deformation in adhesives, known as ratcheting. This response, while critical to the understanding of adhesive behavior, is not yet fully understood. This research studies the ratcheting behavior in adhesively bonded scarf joints. A scarf joint was chosen because of its ability to provide nearly uniform shear stress across the joint, and minimal normal stress. Two adhesives were used, a toughened adhesive (EA9696), and a less tough adhesive (FM300-2). The results from scarf joints differed from those found with bulk coupons. In monotonic testing FM300-2 yielded in thin bonds but didn't in bulk coupons. EA9696 yielded 5 times more in thin bonds than it did in bulk coupons. This led to larger plastic deformation in scarf joints than bulk coupons during creep and ratcheting tests. Scarf joints also experienced nonlinear behavior at lower stress levels in thin bonds than they did in bulk. When scarf joints were ratcheted in tension only, both adhesives obeyed linear viscoelastic response. Strain growth scaled linearly with mean stress and plastic strain scaled linearly with the maximum strain experienced in the adhesive. At lower stress levels (20% shear strength) both adhesives continued to behave as expected for fully reversed loading. There was no significant change in strain. At higher stress levels (50% shear strength), both adhesives accumulated positive plastic strain and EA9696 accumulated positive viscoelastic strain from reversed loading. The plastic strain was higher for fully reversed loading than it was for any other stress ratio (τmin/τmax). This phenomenon was determined to be caused by the normal stress in scarf coupons, and because the adhesives behave differently in tension and compression. Bulk coupons have been shown to produce a similar viscoelastic response during reversed loading, but the plastic response observed is novel.
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Details
- Title
- Effect of cyclic shear loading on thin bonded adhesives
- Creators
- Michael D. Krause
- Contributors
- Lloyd V Smith (Advisor) - Washington State University, Mechanical and Materials Engineering, School of
- 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
- Identifiers
- 99900890779501842
- Language
- English
- Resource Type
- Thesis