Title : Study on Impact and Fatigue Properties of Butt and Single Lap Joint Adherend by Epoxy Resin Enhanced by Dispersed Core Shell Rubber Particles
Epoxy adhesives have been widely used in a variety of fields, which require the lightweight joints and joints of different martials, such as aircraft, automotive and wind turbine blades. Core shell rubber (CSR) particle is one of modifier to improve toughness of epoxy adhesives. The CSR particles have a rubber core and is covered with a compatibilizer copolymer shell. It has been known that the static strength of the adhesive joint using it is improved when CSR particles are added into the adhesive. However, the effect of the modification with the CSR particles on the impact and fatigue properties has not been known in detail, while they are expected for many practical applications. The purpose of this study is to investigate quantitative improvement rates of impact and fatigue properties of steel joints adherend by epoxy resin modified with CSR particles. Three types of adhesives of which rubber contents were about 3.60wt% and 3.85wt% for the modification and also 0wt% of unmodified one for comparison were prepared as the materials of adhesives to make the single lap joints in order to investigate the effect of the modification. Impact load was applied to the specimen of butt joints of which length, width and thicknesses was 90mm, 45mm and 20mm respectively, by hitting hammer moved from upper position like a pendulum. Cyclic loading was repeated to specimen of single lap joints under three-point bending, where cyclic stress ratio and frequency were R = 0.1 and f = 5.0Hz, respectively in order to measure the fatigue life and residual strain. The maximum cyclic stress was set to 70%, 75% and 80% of average static bending strength. The test results showed that the impact strength of adhesive joints were improved about 12.9% and 29.1% and the fatigue lives of those were also improved about 1.79 times and 3.51 times, respectively, when the rubber content of added CSR particles was 3.60wt% and 3.85wt%, compared to those by unmodified adhesives. The residual strain at the same number of cycles was decreased about 25.7% and 45.7% when rubber content of added CSR particles was 3.60wt% and 3.85wt%, respectively compared to as well, while the nominal residual strain was increased with increase of the number of cycles. These results showed that the crack propagations of adhesives were prevented when CSR particles were added because the residual strains of adhesives were usually related with crack propagation. The rough fracture surfaces of specimens of butt joints adherend by epoxy resin modified with CSR particles were observed suggesting the traces of the plastic deformation of adhesives around CSR particles and between CSR particles. It is said that the energy release of epoxy adhesives around the CSR particles was contributed to the improvement of the impact property of adhesive joints.
What will audience learn from your presentation
- Quantitative improvement rates in impact strength and fatigue life of steel joints adherend by epoxy resin by dispersed by CSR particles.
- What contributes to the improvement of the impact and fatigue properties of the steel joints adherend by epoxy resin by dispersed by CSR particles.
- Influence of the modification with the CSR particles on the fracture surface and the residual strain of the steel joints.