Questions | Wood, Composite and Transparent Plastic Structures

Fill in the Blanks

1. The reference wood for aircraft structures is __________.

2. Aviation-quality wood is usually __________ sawn to minimize __________.

3. The maximum slope of the grain for aviation-grade lumber is __________ to __________.

4. __________ plywood, covered with aircraft fabric may be used as the external skin on some aircraft.

5. To prevent wood structure rotting, it should be treated with a(n) __________ sealer.

6. The best finish for internal wood structure is a good coat of high-quality ___________.

7. A splayed patch cannot be used in plywood skin that is more than __________-inch thick.

8. The taper for a splayed patch is _____:1.

9. __________ is the name given to aromatic polymide fibers, such as Kevlar.

10. Because of its many excellent properties, Aramid is ideal for aircraft parts that are subject to

__________ and __________.

11. The tightly woven edge produced by the weavers to prevent the edges from raveling is referred to as the __________ edge.

12. The __________ is at a 45° angle to the warp threads.

13. Material in which all of the major fibers run in one direction, giving strength in that direction, are known as __________.

14. Chopped fibers that are compressed together are often called __________.

15. Epoxy resin matrices are two-part systems consisting of a __________ and a __________. The __________ acts as a curing agent by initiating a chemical reaction to harden the epoxy.

16. Pre-impregnated fabrics, or pre-pregs, are simply fabrics that have the __________ system already impregnated into the fabric.

17. Pre-preg fabrics must be kept __________ to prevent the resin from curing.

18. __________ are a popular thixotropic agent for use with thermosetting resins to give the resin good body with a minimum of weight.

19. In addition to microballoons, __________ and __________ may be used as filler material when repairing composite structures.

20. __________ foam can be used with either epoxy or polyester resin.

21. When working with solvents and resins, it is important to take precautions against __________ and to always work in __________ areas.

22. The __________ is a simple method of detecting delaminations close to the surface of a part.

23. To detect internal flaws or areas of delamination a(n) __________ may be used.

24. __________ locates flaws by temperature variations at the surface of a damaged part.

25. Scissors with special steel blades with serrated edges are used to cut through __________ fabric.

26. Whenever possible composite materials should be __________ with wood when drilling.

27. __________ (Steel, Carbide or Diamond) drills work on all types of composites and have long life.

28. While sanding, drilling, or trimming composite materials __________ must be worn to prevent breathing toxic fumes or dust.

29. Special brad point drills are available for drilling __________ (what type) composites.

30. Air-driven __________ are the best tools to use to remove damaged honeycomb core material from an aircraft structure.

True or False

1. Sandpaper should not be used to prepare a surface for gluing. (TRUE/FALSE)

2. The highest points inside an aircraft structure are the most likely places for wood deterioration to begin. (TRUE/FALSE)

3. If wood comes up in small chunks rather than splinters when it is picked with the point of a knife blade, it may be considered to be good. (TRUE/FALSE)

4. A wing spar may not be spliced under the fitting for a lift strut. (TRUE/FALSE)

5. Carbon fiber has high compressive strength, but promotes galvanic corrosion when bonded to aluminum or steel. (TRUE/FALSE)

6. The strength of a fiber is perpendicular to the direction that the threads run. (TRUE/FALSE)

7. The threads which run the length of the fabric as it comes off the bolt are referred to as the warp. (TRUE/FALSE)

8. Fabrics are less resistant to fiber breakout, delamination, and more damage tolerant than unidirectional materials. (TRUE/FALSE)

9. Thermoplastic and thermosetting resins have great strength in themselves, and need not be reinforced with paper, cloth, or other filaments. (TRUE/FALSE)

10. A thermoplastic resin will not change shape if sufficiently re-heated while a thermosetting resin will change shape if re-heated. (TRUE/FALSE)

11. When the shelf life of a pre-preg fabric has expired it may not be used for aircraft applications. (TRUE/FALSE)

12. The ribbon direction of a honeycomb core is the direction in which the honeycomb cannot be pulled apart. (TRUE/FALSE)

13. Closed cell styrofoam should be used with polyester resin only. (TRUE/FALSE)

14. The procedures for mixing resin systems are very important. (TRUE/FALSE)

15. Pot life is the working life of a resin batch while shelf life is the storage life of unopened resin containers. (TRUE/FALSE)

Knowledge Application Questions

1. What type of wood should be used when splicing or reinforcing plywood webs?

2. Name at least four different types of defects found in wood.

3. What are the three types of glues used in modern aircraft construction and repair?

4. Why should the various pieces of wood being joined be kept in the same room for at least 24 hours prior to joining?

5. Why is it important to consider the open-assembly time when gluing wooden structures?

6. Why is it important to apply the proper clamping pressure to a glue joint?

7. What minimum curing temperature should be observed when joining wood with various adhesives?

8. When inspecting wood structures, why might it be important to consider stains and discolored areas?

9. In what areas are splices to a wood spar prohibited?

10. Describe the characteristics of a scarf joint.

11. What are the two primary uses for plywood in aircraft construction?

12. Provide examples of at least three types of plywood skin repairs.

13. What should be done to prevent a 1 wood patch and the pressure plate from sticking together if glue is extruded from the joint?

14. Why are lightweight steel bushings sometimes used in wooden structures?

15. What is the purpose of large surface area washers when used on wooden structures?

Multiple Choices Questions

1. Laminated wood spars may be substituted for solid rectangular wood spars
a. only in certain instances where the primary load is shared by one or more other original structural member.
b. only upon specific approval by the manufacturer or the FAA.
c. if the same quality wood is used in both.

2. The strength of a well designed and properly prepared wood splice joint is provided by the
a. bearing surface of the wood fibers.
b. glue.
c. reinforcement plates.

3. Where is information found concerning acceptable species substitutions for wood materials used in aircraft repair?
a. Technical Standard Orders.
b. Aircraft Specifications or Type Certificate Data Sheets.
c. AC 43.13-1B.

4. In cases of elongated boltholes in a wood spar or cracks in the vicinity of boltholes,
a. it is permissible to ream the hole, plug with hardwood, and redrill.
b. a new section of spar should be spliced in or the spar replaced entirely.
c. the spar may be reinforced by using hardwood reinforcing plates.

5. A faint line running across the grain of a wood spar generally indicates
a. compression failure.
b. shear failure.
c. decay.

6. Which statement about wood decay is correct?
a. Decay that occurs before the wood is seasoned does not affect the strength of the finished piece.
b. A limited amount of certain kinds of decay is acceptable in aircraft woods since decay affects the binding between the fibers and not the fibers themselves.
c. Decay is not acceptable in any form or amount.

7. Which of the following conditions will determine acceptance of wood with mineral streaks?
a. Local irregularities do not exceed limitations specified for spiral and diagonal grain.
b. Careful inspection fails to reveal any decay.
c. They produce only a small effect on grain direction.

8. The I beam wooden spar is routed to
a. reduce weight.
b. increase strength.
c. obtain uniform strength.

9. Pin knot clusters are permitted in wood aircraft structure provided
a. no pitch pockets are within 12 inches.
b. they produce a small effect on grain direction.
c. they have no mineral streaks.

10. The cantilever wing uses
a. the skin to carry most of the load to the wing butt.
b. no external bracing.
c. external struts or wire bracing.

11. Laminated wood is sometimes used in the construction of highly stressed aircraft components. This wood can be identified by its
a. similarity to standard plywood construction.
b. parallel grain construction.
c. perpendicular grain construction.

12. When patching a plywood skin, abrupt changes in cross sectional areas which will develop dangerous stress concentration should be avoided by using
a. circular or elliptical patches.
b. square patches.
c. doublers with any desired shaped patches.

13. Glue deterioration in wood aircraft structure is indicated
a. when a joint has separated and the glue surface shows only the imprint of the wood with no wood fibers clinging to the glue.
b. by any joint separation.
c. when a joint has separated and the glue surface shows pieces of wood and/or wood fibers clinging to the glue.

14. Compression failures in wood aircraft structures are characterized by buckling of the fibers that appear as streaks on the surface
a. at right angles to the growth rings.
b. at right angles to the grain.
c. parallel to the grain.

15. Sandwich panels made of metal honeycomb construction are used on modern aircraft because this type of construction
a. may be repaired by gluing replacement skin to the inner core material with thermoplastic resin.
b. has a high strength to weight ratio.
c. is lighter than single sheet skin of the same strength and is more corrosion resistant.

16. (1) When performing a ring (coin tap) test on composite structures, a change in sound may be due to damage or to transition to a different internal structure.
(2) The extent of separation damage in composite structures is most accurately measured by a ring (coin tap) test.

Regarding the above statements,
a. only No. 1 is true.
b. only No. 2 is true.
c. both No. 1 and No. 2 are true.

17. Which of these methods may be used to inspect fiberglass/honeycomb structures for entrapped water?
1. Acoustic emission monitoring.
2. X-ray.
3. Backlighting.

a. 1 and 2.
b. 2 and 3.
c. 1 and 3.

18. When balsa wood is used to replace a damaged honeycomb core, the plug should be cut so that
a. the grain is perpendicular to the skin.
b. the grain is parallel to the skin.
c. it is about 118-inch undersize to allow sufficient bonding material to be applied.

19. When repairing puncture type damage of a metal faced laminated honeycomb panel, the edges of the doubler should be tapered to
a. whatever is desired for a neat, clean appearance.
b. 100 times the thickness of the metal.
c. two times the thickness of the metal.

20. One of the best ways to assure that a properly prepared batch of matrix resin has been achieved is to
a. perform a chemical composition analysis.
b. have mixed enough for a test sample.
c. test the viscosity of the resin immediately after mixing.

21. Composite inspections conducted by means of acoustic emission monitoring
a. pick up the "noise" of corrosion or other deterioration occurring.
b. create sonogram pictures of the areas being inspected.
c. analyze ultrasonic signals transmitted into the parts being inspected.

22. What precaution, if any, should be taken to prevent corrosion inside a repaired metal honeycomb structure?
a. Prime the repair with a corrosion inhibitor and seal from the atmosphere.
b. Paint the outside area with several coats of exterior paint.
c. None. Honeycomb is usually made from a man made or fibrous material which is not susceptible to corrosion.

23. One method of inspecting a laminated fiberglass structure that has been subjected to damage is to
a. strip the damaged area of all paint and shine a strong light through the structure.
b. use an eddy current probe on both sides of the damaged area.
c. use dye penetrant inspection procedures, exposing the entire damaged area to the penetrant solution.

24. When inspecting a composite panel using the ring test/tapping method, a dull thud may indicate
a. separation of the laminates.
b. an area of too much matrix between fiber layers.
c. less than full strength curing of the matrix.

25. How many of the following are benefits of using microballoons when making repairs to laminated honeycomb panels?
1. Greater concentrations of resin in edges and comers
2. Improved strength to weight ratio.
3. Less density.
4. Lower stress concentrations.

a. Three.
b. Four.
c. Two.

26. The length of time that a catalyzed resin will remain in a workable state is called the
a. pot life.
b. service life.
c. shelf life.

27. A category of plastic material that is capable of softening or flowing when reheated is described as a
a. thermoset.
b. thermoplastic.
c. thermocure.

28. The classification for high tensile strength fiberglass used in aircraft structures is
a. S.
b. G.
c. E.

29. Which is an identifying characteristic of acrylic plastics?
a. Zinc chloride will have no effect.
b. Has a yellowish tint when viewed from the edge.
c. Acetone will soften plastic, but will not change its color.

30. Superficial scars, scratches, surface abrasion, or rain erosion on fiberglass laminates can generally be repaired by applying
a. a piece of resin impregnated glass fabric facing.
b. one or more coats of suitable resin (room temperature catalyzed) to the surface.
c. a sheet of polyethylene over the abraded surface and one or more coats of resin cured with infrared heat lamps.

Wood, Composite and Transparent Plastic Structures question papers for aircraft licence exam

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