CCT CCT Surface Preparation & Bonding 2 — Questions and Answers
Question 1: What adhesive form is most often used for structural composite bonding in aerospace applications?
- Film adhesive (e.g., Redux or EA9696) (Correct answer)
- Liquid epoxy mixed on-site
- Hot glue
- Rubber cement
Correct answer: Film adhesive (e.g., Redux or EA9696)
Film adhesives provide uniform bondline thickness and consistent mechanical properties critical for aerospace structures.
Question 2: What is bondline thickness, and why is it controlled during adhesive bonding?
- The cured adhesive gap between adherends; controlled to ensure designed strength and prevent starved or thick bonds (Correct answer)
- The total thickness of the composite laminate
- The depth of surface abrasion scratches
- The weight of adhesive per square inch
Correct answer: The cured adhesive gap between adherends; controlled to ensure designed strength and prevent starved or thick bonds
Too thin a bondline (starved) reduces strength, while too thick reduces stiffness and increases void content.
Question 3: What is the function of a bond fixture or tooling during adhesive cure?
- To maintain part geometry and apply uniform pressure during cure (Correct answer)
- To heat the adhesive with electrical resistance
- To apply chemical catalyst to the adhesive
- To weigh the assembly during cure
Correct answer: To maintain part geometry and apply uniform pressure during cure
Bond fixtures hold mating parts in alignment and apply the clamping pressure needed for proper adhesive flow and cure.
Question 4: During a co-bond operation, what is being joined?
- A cured laminate to an uncured laminate using adhesive, cured simultaneously (Correct answer)
- Two fully cured laminates bonded with room-temperature adhesive
- Two metal fittings bolted together
- A composite skin to a foam core with rivets
Correct answer: A cured laminate to an uncured laminate using adhesive, cured simultaneously
In co-bonding, one part is already cured and the other (with or without film adhesive) is cured in the same cycle.
Question 5: What type of failure mode indicates that the adhesive was stronger than the surface preparation?
- Cohesive failure within the adhesive layer
- Adhesive failure at the bondline interface (Correct answer)
- Laminate delamination away from the bond
- Porosity within the core
Correct answer: Adhesive failure at the bondline interface
Adhesive (interfacial) failure means the adhesive separated from the substrate surface, indicating poor surface prep.
Question 6: Which environmental condition most negatively impacts adhesive bond strength during cure?
- High humidity causing moisture contamination at the bondline (Correct answer)
- Low ambient light
- High altitude
- Vibration from nearby equipment
Correct answer: High humidity causing moisture contamination at the bondline
Moisture at the bondline can prevent proper adhesive wetting and cause hydrolytic degradation of the bond.
CCT CCT Surface Preparation & Bonding 2
What adhesive form is most often used for structural composite bonding in aerospace applications?