Explanations: Sheet Metal and Non-Metallic Structures Flashcards
A properly designed rivet joint will have the major part of load in the rivets as what?
Shear load.
What are Lockbolt/Huckbolt fasteners?
A two-piece fastener that consists of a hardened metal pin and a metal collar that swages into the grooves of the pin, forming a specific, measured clamp force to hold assembled parts together.
The head of a shop head rivet should have a diameter and thickness of what?
It should have a diameter of 1-1/2 times the rivet shank diameter and a thickness of 1/2 of the shank diameter.
What are HI-LOK fasteners?
They are a new form of Hi-Shear fastener that can be installed with ordinary hand tools rather than requiring the special riveting tools.
The pin is installed in an interference-fit hole and the collar screwed down over the threaded end. The pin is held with an Allen wrench and the collar is screwed down, using an open-end wrench until the proper torque is reached. At this point, the hex shear-nut portion of the collar will break off.
What are the advantages of HI-LOK fasteners?
Light weight, high fatigue resistance, high strength, and inability to be over-torqued.
What are Dzus fasteners, and how are they identified?
They are the type of fasteners that are used to install instruments. They pop out automatically with about one turn.
They are identified by marks on the head of the stud. The letter identifies the type of head, a number identifies the body diameter in 1/16-inch increments, and another number identifies the stud length in hundredths of an inch.
What are rivnuts?
A special type of blind rivet whose shank has internal threads.
When the rivnut is upset in a piece of thin sheet metal, the threaded shank acts as a nut to receive a machine sew.
Rivnuts were originally designed to attach deicer boots to thin sheet metal wing and empennage leading edges.
What are CherryMAX and Olympic-Lok rivets?
types of rivets installed using a special pulling tool that swells the taper at the end of the shank as the pulling stem is pulled. Continued pulling breaks off the stem and leaves part of it in the hollow shank to reinforce it.
What problem exists with carbon/graphite as a structural material?
The fact that aluminum alloys in contact with it will corrode.
For this reason, fasteners used with carbon/graphite must be made of a corrosion-resistant material such as titanium or corrosion-resistant steel.
What is the backlighting method?
It is done by removing all of the paint from the surface and shining a strong light on one side of the panel and examining from the other side for any dark areas that would indicate entrapped water.
How do you repair a puncture to a metal-face laminated honeycomb panel?
Cut a piece of aluminum alloy the same thickness or thicker than the original face and taper the edges of this patch back to a ratio of about 100 to one.
How do you utilize the extra prepared matrix resin when repairing a composite?
You make and identical test layup to the repair, using the same cure time, pressure, and temperature as is used on the actual repair. The test sample should have the same finished characteristics as the repair.
What is acoustic emission monitoring?
A method of inspecting composite materials for the presence of active corrosion. A sensitive microphone and amplifier are used with the microphone held against the surface being inspected. If corrosion is present, the noise caused by the bubbles generated by the corrosion activity will be heard as a hissing sound. When the panel is heated to about 150 degrees F, the noise cause by disbonding of the adhesive will be heard as a crackling sound.
What is tap testing on composites?
A common technique used for the detection of delamination and/or disbond. The method is accomplished by tapping the inspection area with a solid round disk or lightweight hammer-like device and listening to the response of the structure to the hammer. A clear, sharp ringing sound is indicative of a well-bonded solid structure, while a dull or thud-like sound indicates a discrepant area.
What is E-glass versus S-glass?
E, or electrical glass, has a high dielectric strength and is designed primarily for electrical insulation.
S, or structural glass, has high tensile strength and is used for structural applications.
What effect will zinc chloride have on cellulose acetate plastic vs acrylic plastic?
It will cause the cellulose acetate plastic to turn milky, while it will have no effect on acrylic plastic.
Explain what warp, bias, and fill are.
Warp threads are the threads that run the length of the piece of fabric and are generally the strongest.
Bias runs diagonally.
Fill threads run across the material.
What is a warp clock?
a template with eight arms 45 degrees apart that allows you to orient the warp threads in the various plies of a laid up repair in the direction specified by the aircraft structural repair manual.
What are prepregs?
Preimpregnated materials are fabrics that are uniformly impregnated with the matrix resins.
They are rolled up and stored in a refrigerator to prevent their curing until they are to be used. One side of the material is covered with a plastic backing to prevent its sticking together while it is stored.
To make a prepreg composite layup, cut the plies to size, remove the plastic backing, lay the plies up observing the correct ply orientation, and apply pressure and external heat.
Why is water the only acceptable cutting fluid for machining composite laminates?
improper cutting fluids would contaminate the material and prevent subsequent bonding.
After a damaged fiberglass laminate surface is repaired using a putty consisting of a compatible resin and clean, short glass fibers, and the resin has cured, what final action do you perform?
sand the resin smooth.
Where can details on what fiberglass damage can and cannot be repaired be found?
AC 43. 13-1B
What repair methods may be used to repair fiberglass damage that extends completely through a laminated sandwich structure?
a stepped-up joint or a scarfed-joint, both which are described in the AC 43. 13-1B.
