AFAB 120 EXAM WITH 100%
CORRECT ANSWERS
List precautions when sanding and compressing composite structures - Answer-
Standard composite safety procedures call for wearing a dust mask when sanding.
If sanding a part on the aircraft, be sure the aircraft is grounded. Static electricity can
cause combustion, and grounding the aircraft and the cart can prevent this.
Why we perform vacuum leaks - Answer-To make sure air is not leaking into the
laminate.
4 typical problems you will run into when vacuuming a composite part - Answer-Gaps in
the sealant tape, fabric through the sealant tape, dirty surface, cuts in the bagging
material
Describe the difference between step curing, ramp & soap curing - Answer-Step curing
requires the technician to make heat adjustments at certain time intervals with a
manually operated controller.
Ramp & soap curing is controlled by a programmable controller which produces a more
sophisticated and accurate curing than the step curing process.
What is hot bond equipment? Why is it important? - Answer-A heat blanket, heat gun,
heat lamp, ovens, autoclaves.
Heat blanket: applying heat to a composite component for repair work.
Heat gun: a heat blanket might not be flexible enough to conform to the shape of the
part. If this is the case, you can build a structure to hold in heat, then use a heat gun
with a hot bonding machine to apply the heat.
Heat lamp: heat lamps can be used satisfactorily to accelerate room temperature resin
cures.
Ovens: offer controlled, uniform temperature over all surfaces.
Autoclaves: are used in manufacturing to produce very strong, compressed components
Limitations heat blankets have? - Answer-Using an oversized heat blanket can draw too
much current for the machine to handle
When using more than one heat blankets exercise precautions (use heat blankets that
are the same size/use same amount of wattage per square inch, monitor temperature of
heat blanket that does not have the thermocouple with digital thermometer/solid-state
recorder/any device, touch blanket to determine if hotter or cooler than the other, use
, heat blankets with same materials/environment, never leave process unattended, use
thermostatically controlled heat blankets
Regular vs advanced composites? - Answer-Regular: 2 or more materials combined to
form a structure that is much stronger than the individual components
Advanced composites: the result of combining developments in chemical bonding
formulas with new or existing forms of solid structural materials to form the high
strength, light-weight components used in aircraft
List 4 or more advantages/disadvantages of composites? - Answer-Advantages:
High strength-to-weight ratio
Strong as metal part but with weight savings
Does not corrode as sheet metal does
Very flexible (resisting vibrations) eliminating stress fatigue found in metal structures\
Disadvantages:
Expensive
Moisture can be a problem when not fully enclosed in resin
Can cause corrosion when in contact with aluminum
Repairing can be difficult and takes longer
Define the reinforcement materials advantages and disadvantages (4 or more) -
Answer-Reinforcement materials: fiber glass, KEVLAR (aramid), carbon fiber
Carbon fiber advantages: high strength, electrically conductive, high fatigue resistance,
low thermal expansion coefficients
Carbon fiber disadvantages: less impact resistance, corrosive when bonded with
aluminum, they can crack/splinter, more brittle than kevlar
Fiberglass advantages: low cost, electrical properties, shear properties, picks up
moisture
Fiberglass disadvantages: less strength, fragile material, hard to maintain, not heat
resistant
KEVLAR advantages: 43% lighter and 2x stronger than fiberglass; toughness, flexible,
absorbs stress
KEVLAR disadvantages: Weak in compression; difficult to cut, absorbs water if not
sealed, stretches, difficult to drill into
Role of the matrix in a composite? - Answer-Supports the fibers giving it extra strength.
Advantages and disadvantages of an epoxy resin? - Answer-Advantages: easily cured
at room temperature, resins are extremely flexible, exhibit good adhesive
characteristics, are very dimensionally stable
Disadvantages: Expensive, Not suitable for all areas in an aircraft, Not good with other
chemicals, Not water resistant
CORRECT ANSWERS
List precautions when sanding and compressing composite structures - Answer-
Standard composite safety procedures call for wearing a dust mask when sanding.
If sanding a part on the aircraft, be sure the aircraft is grounded. Static electricity can
cause combustion, and grounding the aircraft and the cart can prevent this.
Why we perform vacuum leaks - Answer-To make sure air is not leaking into the
laminate.
4 typical problems you will run into when vacuuming a composite part - Answer-Gaps in
the sealant tape, fabric through the sealant tape, dirty surface, cuts in the bagging
material
Describe the difference between step curing, ramp & soap curing - Answer-Step curing
requires the technician to make heat adjustments at certain time intervals with a
manually operated controller.
Ramp & soap curing is controlled by a programmable controller which produces a more
sophisticated and accurate curing than the step curing process.
What is hot bond equipment? Why is it important? - Answer-A heat blanket, heat gun,
heat lamp, ovens, autoclaves.
Heat blanket: applying heat to a composite component for repair work.
Heat gun: a heat blanket might not be flexible enough to conform to the shape of the
part. If this is the case, you can build a structure to hold in heat, then use a heat gun
with a hot bonding machine to apply the heat.
Heat lamp: heat lamps can be used satisfactorily to accelerate room temperature resin
cures.
Ovens: offer controlled, uniform temperature over all surfaces.
Autoclaves: are used in manufacturing to produce very strong, compressed components
Limitations heat blankets have? - Answer-Using an oversized heat blanket can draw too
much current for the machine to handle
When using more than one heat blankets exercise precautions (use heat blankets that
are the same size/use same amount of wattage per square inch, monitor temperature of
heat blanket that does not have the thermocouple with digital thermometer/solid-state
recorder/any device, touch blanket to determine if hotter or cooler than the other, use
, heat blankets with same materials/environment, never leave process unattended, use
thermostatically controlled heat blankets
Regular vs advanced composites? - Answer-Regular: 2 or more materials combined to
form a structure that is much stronger than the individual components
Advanced composites: the result of combining developments in chemical bonding
formulas with new or existing forms of solid structural materials to form the high
strength, light-weight components used in aircraft
List 4 or more advantages/disadvantages of composites? - Answer-Advantages:
High strength-to-weight ratio
Strong as metal part but with weight savings
Does not corrode as sheet metal does
Very flexible (resisting vibrations) eliminating stress fatigue found in metal structures\
Disadvantages:
Expensive
Moisture can be a problem when not fully enclosed in resin
Can cause corrosion when in contact with aluminum
Repairing can be difficult and takes longer
Define the reinforcement materials advantages and disadvantages (4 or more) -
Answer-Reinforcement materials: fiber glass, KEVLAR (aramid), carbon fiber
Carbon fiber advantages: high strength, electrically conductive, high fatigue resistance,
low thermal expansion coefficients
Carbon fiber disadvantages: less impact resistance, corrosive when bonded with
aluminum, they can crack/splinter, more brittle than kevlar
Fiberglass advantages: low cost, electrical properties, shear properties, picks up
moisture
Fiberglass disadvantages: less strength, fragile material, hard to maintain, not heat
resistant
KEVLAR advantages: 43% lighter and 2x stronger than fiberglass; toughness, flexible,
absorbs stress
KEVLAR disadvantages: Weak in compression; difficult to cut, absorbs water if not
sealed, stretches, difficult to drill into
Role of the matrix in a composite? - Answer-Supports the fibers giving it extra strength.
Advantages and disadvantages of an epoxy resin? - Answer-Advantages: easily cured
at room temperature, resins are extremely flexible, exhibit good adhesive
characteristics, are very dimensionally stable
Disadvantages: Expensive, Not suitable for all areas in an aircraft, Not good with other
chemicals, Not water resistant
