Airframe Structures: Sheet Metal & Non-metallic Structures 🔊 Flashcards
What is the grip length of a rivet?
It is the combined thickness of the material to be joined
Where are special rivets, such as Huck or Cherry lock rivets located?
They are used in places where access to both sides of the riveted structure is impossible or where limited space will not permit the use of a bucking bar. (also known as blind rivets)
What is bonded honeycomb (sandwich) construction?
It is a laminar construction consisting of a combination of alternating dissimilar materials; assembled and fixed in relation to each other so that the properties of each can be used to attain specific structural advantages for the whole assembly while reducing weight.
What type of materials are used in honeycomb construction?
Stainless steel, titanium, magnesium, plywood, resin impregnated paper, E-glass, nylon in various combinations
Where are sandwich construction assemblies used?
Bulkheads, control surfaces, fuselage panels, wing panels, radomes, empennage skins, or shear webs
What procedures should be used to prevent damage to the hole when drilling through Plexiglas?
Plexiglas should be backed with wood and the feed slowed. The drill bit should be modified to a 60° tip angle. The cutting edge to zero-rake angle and the back lip clearance angle increased 12-15°.
What calculations must be made when bending sheet metal?
Setback and bend allowance
What factors are used to determine setback?
Radius of the bend and thickness of the material. (Setback = radius + thickness)
When bending sheet metal, how should the grain be in relation to the bend?
Perpendicular to the bend
What is a bend tangent line?
The line at which the metal starts to bend
What is a joggle?
An offset near the edge of a piece of sheet metal to allow clearance for a sheet or extrusion
What are several methods used in forming sheet metal?
Folding, bumping, crimping, shrinking, and stretching
What kind of metal forming is done by bumping?
Compound curves
What is crazing and how does it occur?
Hairline cracks in the surface plastic. Uneven heating causing one side to expand more than the other, subjecting plastics to large stresses, and exposure to harmful solvents
Briefly describe the anodizing process and what purpose it serves.
Aluminum alloys are placed in an electrolytic bath which causes a thin film of hydroxide to form on the surface. The coating provides excellent resistance to corrosion, but it is also an excellent bond for paint.
What are the proper dimensions for the shop head of a rivet?
1.5 times the diameter in width and .5 times the diameter in height after bucking
When inspecting Plexiglas, what should you look for?
Crazing and discoloration
What causes honeycomb structure to delaminate?
Moisture
What are the acceptable repair methods for bonded honeycomb structure that has been damaged?
A potted repair or a laminated glass fabric cloth overlay, if the damage exceeds the repair limitations of the potted compound method.
What size drill should be used for the common shank rivet diameters of 3/32 inch, 4/32 inch, and 5/32 inch?
3/32 = number 40; 4/32 = number 30; 5/32 = number 21
What is used for hole filling in a bonded honeycomb repair?
Potting compound
What is a lightning hole?
They are cut into rib sections, fuselage frames, and other structural parts to decrease weight.
What special precautions should be observed when repairing a radome?
Repair must retain its strength and electrical transparency.
What is a warp line?
A highlighted strand in the fabric used for ply orientation.
What does “pot life” mean?
The length of time a resin will remain workable after the catalyst is added.
What is a Barcol hardness test?
A device that pushes a spike into material such as composites. The depth of penetration can be measured to determine if resins in the composite have cured.
What is done to honeycomb before repairing?
Remove damaged honeycomb and either replace with potting compound or a honeycomb replacement plug.
What is the difference between thermoplastics and thermosetting plastics?
Thermoplastics can be remelted and reformed. Thermosetting cannot.
When cutting a piece of sheet metal at the edge, and you bend the corners in, what needs to be done?
You must drill a relief hole.
