Composite and Non-metallic
Mechanics of Aircraft Materials
Department of Aerospace Engineering – Faculty of Transportation Engineering
Dr Ly Hung Anh
Trang 2I NTRODUCTION
Since the mid-1950s, the use of magnesium, plastic, fabric, and wood in aircraft construction has nearly disappeared.
Using of aluminum and aluminum alloys for airframe construction:
80 percent of airframes in 1950
About 15 percent today for airframe construction.
Nowadays, the aircraft construction uses more and more the nonmetallic materials such as
reinforced plastics
advanced composites
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Trang 4C OMPOSITE M ATERIALS
A “composite” material is defined as a mixture of different materials or things to enhance the strength, ductility, conductivity or whatever desired
Composition: 2 phases
Composition: 2 phases
Resin: continuous and surrounding other phase.
Reinforcement: surrounded by the resin, to enhance the
Trang 5A DVANTAGES OF C OMPOSITES
High strength to weight ratio
Fiber-to-fiber transfer of stress allowed by chemical bonding
Modulus (stiffness to density ratio) 3.5 to 5 times that of steel or aluminum
Longer life than metals
Higher corrosion resistance
Tensile strength 4 to 6 times that of steel or aluminum
Greater design flexibility
Bonded construction eliminates joints and fasteners
Trang 6Very expensive processing equipment
Lack of standardized system of methodology
Great variety of materials, processes, and techniques
General lack of repair knowledge and expertise
Products often toxic and hazardous
Lack of standardized methodology for construction and
Trang 7C OMPOSITE S AFETY
Composite products can be very harmful to the skin, eyes, and lungs.
Respirator particle protection is very important to
protecting the lungs from permanent damage from tiny glass bubbles and fiber pieces.
Methods of protection:
Methods of protection:
Dust masks
Respirator with dust filters (Charcoal filters)
Supplied air mask and hood
Avoid skin contact with the fibers: by wearing long pants and long sleeves along with gloves or barrier creams.
The eyes protection: using leak-proof goggles (no vent
Trang 8F IBER R EINFORCED M ATERIALS
Purpose of reinforcement: to provide most of the
Particle: square piece of material with their dimensions are equal on all axes.
Whisker:
piece of material with the length greater than the width
usually single crystals
very strong and used to reinforce ceramics and metals.
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Trang 9F IBER R EINFORCED M ATERIALS
Fiber:
single filaments that are much longer than they are wide.
be made of almost any material, and are not crystalline like whiskers
base for most composites
base for most composites
smaller than the finest human hair
normally woven into cloth-like materials
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Trang 10D ISTRIBUTION OF F IBERS ON A L AMINA
Lamina: very thin layer of the resin and the fibers.
Distribution of fibers: 3 ways
Long aligned fibers
Short aligned fibers
Short non-aligned fibers
Short non-aligned fibers
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Trang 11L AMINATED S TRUCTURE
Manufacture: composing many layers or panels with different directions of reinforced fibers.
Purpose: increase the strength in different directions.
Laminate construction is strong and stiff, but heavy. 11
Trang 12S ANDWICH S TRUCTURE
Laminated structure with a core center is called a sandwich structure.
The sandwich laminate is equal in strength, and its weight is much less.
Composition:
Composition:
2 face sheets (lamina sheets)
Core center (honeycomb)
Applications:
Rotor blades of helicopters
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Trang 13F ABRICATION A S ANDWICH P ANEL
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Trang 14H ELICOPTER ’ S R OTOR B LADES
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Trang 15TRANSPARENT PLASTICS
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Trang 16T RANSPARENT P LASTICS
Classification: according to their reaction to heat.
thermoplastic : soften when heated and harden when cooled.
thermosetting: harden upon heating, and reheating has no softening
Laminate transparent plastic: made from transparent plastic face sheets bonded by an inner layer material, usually
Trang 17L AMINATED T RANSPARENT P LASTICS
Stretched acrylic is a type of plastic which before being shaped, is pulled in both directions to rearrange its
molecular structure
Properties:
great resistance to impact
great resistance to impact
Less subject to shatter
Great chemical resistance
Simple edging
Less crazing and scratches detriment.
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Trang 18L AMINATED P LASTIC U SING
Individual sheets of plastic are covered with a heavy masking paper with pressure sensitive adhesion.
Be careful to avoid scratches and gouges
By sliding sheets against one another
By sliding sheets across rough or dirty tables.
store in a cool, dry place away from solvent fumes, heating coils, radiators, and steam pipes.
temperature in the storage room should not exceed 120 °F 18
Trang 19Resin: polymers which the viscosity varies from a waterlike consistency to a thick syrup.
Reinforcement: glass cloths.
Cure or polymerization: use a catalyst, usually benzoyl peroxide.
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Trang 20R EINFORCED P LASTIC
Solid laminates
constructed of three or more layers of resin impregnated cloths “wet laminated” together to form a solid sheet facing or molded shape. Sandwich-type laminates
constructed of two or more solid sheet facings or a molded shape
fiberglass honeycomb or foam-type core Honeycomb cores:
Reinforcement: glass cloths
Resin: polyester or a combination of nylon and phenol
The specific density and cell size varies over a considerable latitude Foam-type cores:
combinations of alkyd resins and metatoluene di-isocyanate
esin forms a bond between the facing and the core. 20
Trang 21R EINFORCED P LASTIC
Properties:
excellent dielectric characteristics
high strength-to-weight ratio
resistance to mildew, rust, and rot
Trang 2222
Trang 23prevent the entrance of dirt, water, or air.
prevent the loss of fluids, gases, or air
absorb vibration, reduce noise, and cushion impact loads.
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Trang 24N ATURAL R UBBER
Natural rubber has better processing and physical properties than synthetic or silicone rubber
Properties:
flexibility, elasticity, tensile strength, tear strength
low heat buildup due to flexing (hysteresis)
low heat buildup due to flexing (hysteresis)
swells and often softens in all aircraft fuels and in many
Trang 25S YNTHETIC R UBBER
Several types: compounded of different materials to give the desired properties
Butyl: a hydrocarbon rubber with:
superior resistance to gas permeation
resistant to deterioration
physical properties are less than those of natural rubber
resistance with oxygen, vegetable oils, animal fats, alkalies, ozone, and weathering
swell in petroleum or coal tar solvents
low water absorption rate and good resistance to heat and low temperature
using temperatures ranging from −65 °F to 300 °F
used with phosphate ester hydraulic fluids (Skydrol), silicone fluids, gases, ketones, and acetones.
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Trang 26S YNTHETIC R UBBER
Buna: Buna-S and Buna-N.
Buna-S rubber :
As water resistant as natural rubber
better aging characteristics
good resistance to heat, but only in the absence of severe flexing
poor resistance to gasoline, oil, concentrated acids, and solvents
used for tires and tubes as a substitute for natural rubber. Buna-N:
outstanding in its resistance to hydrocarbons and other solvents
poor resilience in solvents at low temperature
good resistance to temperatures up to 300 °F
may be procured for low temperature applications down to −75 °F
fair tear, sunlight, and ozone resistance
good abrasion resistance and good breakaway properties
used for oil and gasoline hose, tank linings, gaskets, and seals. 26
Trang 27S YNTHETIC R UBBER
Neoprene:
take more punishment than natural rubber
better low temperature characteristics
exceptional resistance to ozone, sunlight, heat, and aging
less like rubber in some of its characteristics than butyl or
less like rubber in some of its characteristics than butyl or Buna
tear resistance and abrasion resistance is slightly less than natural rubber
superior resistance to oil
poor resistance to aromatic gasolines
used for weather seals, window channels, bumper pads, oil resistant hose, and carburetor diaphragms
recommended for use with Freons™
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Trang 28S ILICONE R UBBER
Silicone rubbers: group of plastic rubber materials made from silicon, oxygen, hydrogen, and carbon.
Properties:
excellent heat stability
very low temperature flexibility (up to 600 °F)
very low temperature flexibility (up to 600 °F)
resistant to temperatures down to −150 °F
good resistance to oils
reacts to both aromatic and nonaromatic gasolines
Applications: Silastic - one of the best known silicones
used to insulate electrical and electronic equipment
used for gaskets and seals in certain oil systems
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