6. Materials & hardware - Q&A

Galvanic action caused by dissimilar metal contact may best be prevented by

• applying a non-porous dielectric material between the surfaces.
• special precautions are not required if they are properly bonded.
• priming both the surfaces with a light coat of zinc chromate primer.

Intergrannular corrosion in structural aluminium alloy parts

• are not likely to occur in parts fabricated from heat-treated sheet aluminium.
• may be detected by the white, powdery deposit formed on the surface of the metal.
• cannot always be detected by surface indications.

Co-axial cables are used

• as they are able to handle high current.
• as the fields due to current flow in the inner and outer cancel each other out.
• as they are protected from electromagnetic interference.

Which fibre to resin (%) ratio for advanced composite wet lay-ups is generally considered the best?

• 60:40.
• 50:50.
• 40:60.

If the cross sectional area of a cable is increased, what will happen to the voltage drop?

• Decrease.
• Increase.
• Stay the same.

Which of the following are generally characteristic of aramid fibre (Kevlar) composites?

• High tensile strength and flexibility.
• Flexibility, stiffness and corrosive effect in contact with aluminium.
• High tensile strength, stiffness and ability to insulate electricity.

On a pre-preg composite

• life can be extended by 12 months if stored above 40 degreesC
• life can be extended by 12 months if stored below 10 degreesC
• no life extension is allowed, it must be used immediately.

Galvanic corrosion is most likely to be most rapid and severe when

• the surface area of the anodic metal is smaller than the surface area of the cathodic material.
• the surface area of the cathodic metal and the anodic material are approximately the same.
• the surface area of the cathodic metal is smaller than the surface area of the anodic material.

When examining a piece of metal through a magnifying glass, hair line cracks would indicate

• crevice corrosion.
• intergrannular corrosion.
• surface corrosion.

Co-axial cables are used

• as they are able to handle high current.
• as the fields due to current flow in the inner and outer cancel each other out.
• as they are protected from electromagnetic interference.

Kevlar and Nomex are types of

• glass fibre composite.
• advanced composite.
• aluminium alloy.

Galvanic action caused by dissimilar metal contact may best be prevented by

• applying a non-porous dielectric material between the surfaces.
• special precautions are not required if they are properly bonded.
• priming both the surfaces with a light coat of zinc chromate primer.