CCT CCT Surface Preparation & Bonding Techniques 2 — Questions and Answers
Question 1: What does 'open time' refer to in adhesive bonding?
- Total time to fully cure the adhesive
- The working time after mixing before the adhesive starts to gel (Correct answer)
- Time to open the adhesive container
- Shelf life of the unmixed adhesive
Correct answer: The working time after mixing before the adhesive starts to gel
Open time is the usable window after adhesive is mixed or applied during which parts must be assembled before gelation prevents proper bonding.
Question 2: Which type of surface contamination is most detrimental to composite adhesive bonding?
- Airborne dust
- Mold release agents and silicone oils (Correct answer)
- Water condensation
- Metallic particles
Correct answer: Mold release agents and silicone oils
Mold release agents and silicone oils are extremely difficult to remove and severely reduce surface energy, causing bond failure even in trace amounts.
Question 3: Which test is used to verify surface cleanliness before bonding composites?
- Tensile test
- Water break test (Correct answer)
- Hardness test
- Bend test
Correct answer: Water break test
The water break test checks surface cleanliness; clean surfaces cause water to sheet evenly, while contaminated surfaces cause water to bead up.
Question 4: What is co-bonding in composite fabrication?
- Bonding two fully cured laminates together with adhesive
- Bonding a cured part to an uncured laminate during the cure cycle (Correct answer)
- Curing two uncured laminates together without adhesive
- Post-cure bonding with mechanical fasteners only
Correct answer: Bonding a cured part to an uncured laminate during the cure cycle
Co-bonding joins a previously cured component to a fresh uncured laminate, curing the assembly together to form the structural joint.
Question 5: What moisture condition is acceptable on composite surfaces before adhesive bonding?
- Up to 5% moisture by weight
- Any amount is acceptable with epoxy adhesives
- Surfaces must be completely dry — moisture causes bond failure (Correct answer)
- Up to 10% moisture by weight
Correct answer: Surfaces must be completely dry — moisture causes bond failure
Moisture on composite surfaces prevents proper adhesive wetting and dramatically reduces bond strength, so surfaces must be thoroughly dried before bonding.
Question 6: Which grit sandpaper is typically recommended for composite surface preparation before secondary bonding?
- 36-grit
- 180 to 220-grit (Correct answer)
- 600-grit
- 1500-grit
Correct answer: 180 to 220-grit
180 to 220-grit sandpaper creates adequate surface roughness for bonding without cutting through surface fibers or causing unnecessary damage.
CCT CCT Surface Preparation & Bonding Techniques 2
What does 'open time' refer to in adhesive bonding?