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Questions and Answers
What is the relationship between the ultimate tensile strength and yield strength in a brittle adhesive?
Why is the single lap shear test a popular method of testing adhesively bonded joints?
Based on the accompanying stress/strain curve, what type of fractures are represented?
Which of the following list of failure modes matches the accompanying figure?
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What is a common factor that can lead to an adhesive failure mode?
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What is the definition of a thermoplastic adhesive?
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What is the purpose of adding particle fillers to an adhesive?
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What is the term for a substance added to an adhesive to improve flexibility, reduce brittleness, and decrease viscosity?
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Study Notes
Adhesive Properties
- In a brittle adhesive, the ultimate tensile strength is much lower than the yield strength.
- The ultimate tensile strength is not always the same as the yield strength.
Testing Adhesives
- The single lap shear test is a popular method for testing adhesively bonded joints because it is cheap and simple to perform.
- The test does not accurately represent the true shear strength of the adhesive, and the adhesive is not subjected to uniform stress across the joint.
- Bond line thickness and load rates can affect the results of the single lap shear test.
Fracture Types
- Based on a stress/strain curve, brittle fractures can be identified.
- Brittle fractures are different from ductile and plastic fractures.
Failure Modes
- Failure modes can be categorized as cohesive, inter-facial, mixed-mode, or brittle.
- Adhesive, cohesive, and substrate failures are different types of failure modes.
- Mixed-mode failure is a type of failure mode.
Causes of Adhesive Failure
- Improper preparation of the substrate surface can lead to adhesive failure.
- Excessive bond-line thickness and defects in the adhesive layer can also cause adhesive failure.
- Consistent bond-line thickness is not a cause of adhesive failure.
Thermoplastic Adhesives
- Thermoplastic adhesives are polymer-based adhesives that are applied in a molten state and cure as they cool.
- They can be reversible upon re-heating.
Particle Fillers
- Particle fillers are often used to reduce costs and increase tack.
- They can also reduce viscosity, but this is not their primary purpose.
Additives
- Plasticizers are substances added to adhesives to improve flexibility, reduce brittleness, and decrease viscosity.
- Wetting agents, thickeners, and hardeners are different types of additives.
Material Properties
- Young's modulus is a measure of stress to recoverable strain of a material.
- Poisson's ratio is a different material property.
Material Laws
- Hooke's Law states that the stress imposed on a material, within its elastic limit, is proportional to the strain produced.
- Young's Law, Ohm's Law, and Brinell's Law are different laws.
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Description
This quiz assesses your knowledge of brittle adhesives and testing methods, including the single lap shear test.
