Adhesives and Glues Flashcards
What role do adhesives and glues play in aircraft structural repair?
Adhesives and glues ensure that the finished strength of any structural repair meets the required specifications.
Why must adhesives used in aircraft construction meet specific performance criteria?
To ensure they are appropriate for wooden structures in aircraft and comply with the Aircraft Maintenance Manual.
What are the common adhesives used in aircraft construction and repair?
Casein glue, plastic resin glue, resorcinol glue, and epoxy adhesives.
Why has casein glue become obsolete for aircraft repairs?
It deteriorates over time when exposed to moisture and temperature variations, and its alkaline nature prevents other glues from curing properly.
What are epoxy adhesives, and what are their advantages in aircraft repairs?
Two-part synthetic resin glues that penetrate evenly into wood, have excellent working properties, and require less attention to joint quality and clamping pressure.
What is plastic resin glue, and why is it not used in modern aircraft repairs?
Also known as urea-formaldehyde adhesive, it deteriorates in moisture and warm, humid environments, leading to failure.
What is resorcinol glue, and why is it commonly used in aircraft repairs?
A two-part synthetic resin glue known for its high water resistance, strength, and durability, making it suitable for aircraft wooden structures.
What are the three important steps for a successful wood joint in aircraft repair?
Proper preparation of the wood surface, use of quality aircraft-standard glue, and good bonding technique consistent with manufacturer instructions.
Why is it important to properly clean and prepare the wood surface before applying adhesive?
To ensure the glue penetrates evenly into the wood, resulting in a strong and durable joint.
Why should sanding not be used to smooth the wood surface before bonding?
Sanding can round the corners and change the flatness, preventing proper mating of the joint surfaces.
What should be done after applying adhesive to the joint surface?
Apply the adhesive evenly, align the joint properly, and apply the correct pressure during the curing process to ensure a strong bond.
What is the recommended clamping pressure for softwood and hardwood when using resorcinol glue?
For softwood, 862 kPa (125 psi) – 1034 kPa (150 psi); for hardwood, 1034 kPa (150 psi) – 1379 kPa (200 psi).
How should the strength of the glued joint be tested?
Place a test sample in a vice, prise the joint apart with a tool, and ensure at least 75% of wood fibers are evenly distributed over the fractured glue surfaces.
