NTSB - AA587
NTSB - AA587
NTSB - AA587
NTSB - AA587
NTSB - AA587
NTSB - AA587
NTSB - AA587
NTSB - AA587
NTSB - AA587
Pilot? Accident Reconstruction
Tollbooth Cameras
Construction Site
Accident Reconstruction
Movie
Pilot Error?
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A300-600 is not fly-by-wire
Maximum rudder deflection at 250 knots (VA)
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AA Training Guide
FAA Pilot’s Handbook of Aeronautical Knowledge
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Pedal force = 10 lbs
Pedal Travel = 1.25 inches
“any combination of flight control usage, including full
deflection of the controls, or gust loads should not create
an excessive air load if the airplane is operated below
mauneuvering speed”
“The Myth of Maneuvering Speed”, Flying Magazine
Types of Fiber Reinforcement
• Whiskers: smallest, nearly perfectly crystalline, extremely
strong and stiff (e.g. graphite, SiC, Al2O3, etc.)
• Fibers: small diameter, polycrystalline or amorphous (e.g.
aramids, glass, carbon, SiC, etc.)
• Wires: relatively large diameter (e.g. steel, tungsten,
molybdenum, etc.)
Modulus (GPa)
1000
carbon
nanotubes
whiskers
100
fibers
wires
10
Diameter
Fiber Weave Patterns
More Complex Fiber Weaves
Prepreg Production
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Prepreg: Tape of thermoset polymer and fiber
reinforcement pre-impregnated with curing agent
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Parts made by “lay-up” of tape
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Must be stored below room temp to slow curing
Hand cut to shape
Manually control orientation
High temperatures and pressures to cure
•
Vacuum bag in autoclave
Hand Lay-up
Lay-up Steps (simple panel)
Tape Placement (7-axis!!)
Applications of Hand Lay-up
www.owenscorning.com/composites/applications
Warpage
Pultrusion
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Used to fabricate
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Rovings or tows
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Long, continuous parts
Constant cross-section
Impregnated with matrix
Pulled through steel die for
shape
Properties often highly
unidirectional
Applications of Pultrusion
www.owenscorning.com/composites/applications/
www.pultruders.com/
Filament Winding
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Used to fabricate
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Hollow parts
Usually radial symmetry
Fibers or tows
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Impregnated with matrix
Continuously wound onto
mandrel
Usually automated winding
equipment
Various winding patterns
used
Excellent strength-to-weight
Very economically attractive
Properties vs. Winding Angle
F
di do
L
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Modulus of Elasticity
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Rule of mixtures estimate
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3-point bending problem
• Ecs=cos q*(EmVm+ EfVf)
Usually concerned with tubes in bending - minimize deflection
FL3
y 
48 EI
I
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 4
d o  d i4
64

Applications of Filament Winding
www.owenscorning.com/composites/applications/
www.advancedcomposites.com
Applications of Filament Winding
www.owenscorning.com/composites/applications/
www.advancedcomposites.com
Resin Transfer Molding
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Used to fabricate
– Intricate 3-D shapes
Fiber preform captured in
closed steel mold
Matrix is injected
Preform may be complex
– Braided,
– Woven, or
– Simple random mat
(SRIM)
Closed tooling provides
good dimensional
stability
Applications of RTM
www.owenscorning.com/composites/applications/consumer/sports.html
Press Forming
(Compression Molding)
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Similar to compression
molding polymers
– Mold heated
– Mold closes and
applies pressure
– Plastic becomes
viscous
– Conforms to mold
shape
May be used for
thermoplastic matrices
Geometry usually limited
Applications of Press Forming
www.owenscorning.com/composites/applications
Injection Molding
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Very similar to injection molding polymers
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Can inject chopped fibers with matrix into closed die
Fibers usually rather short due to screw
Applications of Injection Molding
www.owenscorning.com/composites/applications
Structural & Laminated Composites
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Laminate composite:
• 2-D layered structure designed for high strength in
preferred directions
Sandwich panel:
• Structure with strong outer layers and rigid but light inner
core (e.g. skis)
Applications of Laminates
www.owenscorning.com/composites/applications
http://www.hexcelcomposites.com/Markets/Markets/Sports
www.nikebiz.com
Machining Problems
• Usually must use secondary operations on
composites
• Trim edges
• Cut holes
• Fasteners
• Attachments
• Access for wiring, assembly, maintenance
• Holes will always act as stress concentrations
• Kt  3
• Fatigue often initiated from these points
• Holes need to be drilled as “damage free” as possible
such that concentration does not increase
Machining Problems
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For machining parameters to choose:
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Tool speed
Feed rate
Tool geometry
Coolant
For polymer composites this is difficult
•
Matrix: soft, ductile, hygroscopic
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Fiber: hard, brittle, abrasive
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Want to absorb water in coolant
Tools wear very quickly
Hard to achieve damage free holes and edges
Common Composite Damage
• Fiber breakage
• Broken fibers do not carry load effectively near the hole
• Matrix chip-out
• Geometric discontinuity near hole
• Delamination
• Tool feeds perpendicular to ply, separating from bulk
• Local fiber reinforcement is not balanced
• Matrix overheating
• Locally melt surface
• Results in rough finish, clogged tool
• In some applications load carrying capacity not
important
• Visual rejection still a possibility!
Composite Machining Damage
(SEM Images)
1000x
500x
Fiber Breakage
and Chipout
Matrix Chipout
200x
500x
Matrix
Overheat
Exit Side
Debond