Wood, Composite and Transparent Plastic Structures Flashcards
What are the three forms of wood commonly used in aircraft construction?
Solid, laminated and plywood
What type of wood should be used when splicing or reinforcing plywood webs?
The same type of plywood as originally used
Name at least four different type of defects found in wood?
knots, checks, splits, pitch pockets, cross grain, curly grain, decay, dry rot, etc
Can a section of wood containing a hard knot be used?
yes, within specified limits
What type of glue may have been used in older wooden aircraft construction that requires careful inspection to detect deterioration?
Casein glue
What are the three types of glues used in modern aircraft construction and repair?
Resorcinol glue, phenol-formaldehyde glue and epoxy resin glue.
Is compression wood acceptable for structural repairs?
No
why should the various pieces of wood being joined be kept in same room for at least 24 hours prior to joining?
To allow the moisture content to equalize, thereby minimizing dimensional changes in the wood
why is it important to consider the open-assembly time when gluing wooden structures?
If the maximum open-assembly time is exceeded, the joint may fail since the glue may begin setting up before the joint is assembled
Why is it important to apply the proper clamping pressure to a glue joint?
clamping forces air out of the joint, brings the wood surfaces together evenly and is, in part, responsible for the strength of the glue line
Describe some of the methods used to apply pressure to glue joints?
clamps, nailing strips, power presses, brads, nails, and small screws
What minimum curing temperature should be observed when joining wood with various adhesives?
70 degrees Fahrenheit or as specified by the glue manufacturer
When inspecting wood structures, why might it be important to consider stains and discolored areas?
Stains and discoloration usually accompany decay and or rot
Describe the acceptable methods used to repair elongated bolt holes found in a wooden wing spar?
Remove the section containing the elongated hole and splice in a new section or replace the entire spar
What type of joint is used to splice a solid or rectangular wood spar?
a scarf joint
In what area are splices to a wood spar prohibited?
Under an attachment fitting for the wing root, landing gear, engine-mount, lift, or inter-plane strut
What is the maximum number of splices allowed for any single spar?
Two
Describe the characteristic of a scarf joint?
The pieces to be joined are tapered or beveled on a slope of 1 to 10 or 1 to 12
Why must the beveled cut be accurate on both pieces of wood being repaired with a scarfed joint?
The two pieces must match exactly to ensure a tight glue joint
What are the two primary uses for plywood in aircraft construction?
Gusset (or reinforcing) plates and aircraft skin
Provide examples of at least three types of plywood skin repairs?
Splayed patches, surface patches, plug patches, and scarfed patches
What type of patch should be used to repair small holes in thin plywood skin if the skin is less than 1/10th inch thick?
A splayed patch may be used if the hole can be cleared out to a diameter of less than 15 thicknesses of the skin
What should be done to prevent a plywood patch and the pressure plate from sticking together if glue is extruded from the joint?
Place a piece of waxed paper or vinyl plastic between the patch and the pressure plate
Why are lightweight steel bushings sometimes used in wooden structures?
Bushing prevent the wood from being crushed when bolts are tightened
What is the purpose of large surface area washers when used on wooden structures?
Large washers provide additional bearing area for hardware to help preclude damage to the wood when the hardware is tightened
Name several facing and core materials used in bonded honeycomb structures intended for special applications
Stainless steel, titanium, magnesium, plywood, glass, nylon, and cotton cloth
Describe the construction of a bonded honeycomb structure
It is a laminated structure that has a solid facing bonded to either side of a core consisting of open, six-sided cells
What must be done with a damaged area in a bonded honeycomb structure prior to beginning repairs?
The area must first be inspected to determine the damaged area prior to completely removing the damaged materials
A drill bit used for drilling composites should operate at approximately what speed?
Use an air-driven tool capable of a free speed of up to 20000 RPM
What are the most common causes for delamination of a composite structure?
Sonic vibration, expansion of internal moisture, liquid leakage, and a manufacturing error
What type of defect in, or damage to, a bonded honeycomb structure can be repaired using the potted repair method?
Filling the hole
Name some of the factors that cause crazing in transparent plastic windows and windshields?
Exposure to ultraviolet light, stress, solvents, and improper handling
How should a hole be drilled in Plexiglas to avoid damage to the hole when the drill breaks through to the underside?
Back up the plastic with a piece of wood and feed the drill slowly
