CCT CCT Surface Preparation & Bonding 1 — Questions and Answers
Question 1: What is the primary purpose of abrading a composite surface before bonding?
- To increase surface area and remove contaminants for better adhesion (Correct answer)
- To reduce the weight of the part
- To check for subsurface delaminations
- To apply a primer coat
Correct answer: To increase surface area and remove contaminants for better adhesion
Abrading removes surface contaminants and increases surface area, creating a stronger mechanical bond.
Question 2: Which solvent is most commonly used for wiping composite surfaces prior to bonding?
- Acetone or MEK (methyl ethyl ketone) (Correct answer)
- Hydraulic fluid
- Motor oil
- Water
Correct answer: Acetone or MEK (methyl ethyl ketone)
Acetone or MEK effectively removes oils, grease, and release agents without leaving residue harmful to bond integrity.
Question 3: What does the term 'peel ply' refer to in composite surface preparation?
- A sacrificial fabric layer left on a surface that, when removed, exposes a bondable surface (Correct answer)
- A protective film applied after painting
- A type of fiberglass cloth used for structural reinforcement
- A rubber seal around the vacuum bag
Correct answer: A sacrificial fabric layer left on a surface that, when removed, exposes a bondable surface
Peel ply is applied during layup and removed just before bonding to expose a clean, textured, bondable surface.
Question 4: What is the maximum allowable time between surface preparation and adhesive application according to most aerospace bonding specifications?
- 4 to 8 hours (Correct answer)
- 48 hours
- 72 hours
- 1 minute
Correct answer: 4 to 8 hours
Most bonding specs require adhesive application within 4–8 hours of surface prep to prevent recontamination.
Question 5: Why is a water-break test performed on a composite surface before bonding?
- To verify the surface is clean and free of oil contamination (Correct answer)
- To measure the thickness of the substrate
- To determine the cure state of the resin
- To check for porosity
Correct answer: To verify the surface is clean and free of oil contamination
A clean surface allows water to sheet evenly; if it beads, oil or release agent contamination is present.
Question 6: Which primer is commonly applied to aluminum substrates before structural adhesive bonding in composite assemblies?
- Corrosion-inhibiting epoxy primer (e.g., BR-127) (Correct answer)
- Zinc chromate wash primer only
- Polyurethane topcoat
- Silicone sealant
Correct answer: Corrosion-inhibiting epoxy primer (e.g., BR-127)
BR-127 or similar epoxy primers enhance adhesion and provide corrosion protection on metallic bond surfaces.
CCT CCT Surface Preparation & Bonding 1
What is the primary purpose of abrading a composite surface before bonding?