NTSB - AA587

NTSB - AA587

NTSB - AA587

NTSB - AA587

NTSB - AA587

NTSB - AA587

NTSB - AA587

NTSB - AA587

NTSB - AA587

Pilot? Accident Reconstruction

Construction Site

Tollbooth Cameras

Accident Reconstruction

Movie

Pilot Error?• A300-600 is not fly-by-wire• Maximum rudder deflection at 250 knots (VA)

• Pedal force = 10 lbs• Pedal Travel = 1.25 inches

• AA Training Guide• FAA Pilot’s Handbook of Aeronautical Knowledge

• “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

Mod

ulus

(GPa

)

10

100

1000 carbon nanotubes

whiskers

fibers

wires

Diameter

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.)

Fiber Weave Patterns

More Complex Fiber Weaves

Prepreg Production• Prepreg: Tape of thermoset polymer and fiber

reinforcement pre-impregnated with curing agent• Must be stored below room temp to slow curing

• Parts made by “lay-up” of tape• 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

• Used to fabricate • Long, continuous parts • Constant cross-section

• Rovings or tows • 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 • Used to fabricate

• Hollow parts • Usually radial symmetry

• Fibers or tows • 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

• Modulus of Elasticity• Rule of mixtures estimate• Ecs=cos q*(EmVm+ EfVf)

• Usually concerned with tubes in bending - minimize deflection• 3-point bending problem•

4i

4o

3dd

64I

EI48FLy

L

dodi

F

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• 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)

• 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• Very similar to injection molding polymers

• 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

• 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/applicationshttp://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

• For machining parameters to choose:• Tool speed• Feed rate• Tool geometry• Coolant

• For polymer composites this is difficult• Matrix: soft, ductile, hygroscopic

• Want to absorb water in coolant• Fiber: hard, brittle, abrasive

• 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)

Fiber Breakage and Chipout Matrix Chipout

1000x 500x

Matrix Overheat

Exit Side Debond

200x500x