Transcript Chapter 19
Chapter 19
Manufacturing with
Composites
Composite - Definition
• Structures made of two or more distinct
materials
• The materials maintain their identity during
the process
• The materials maintain their identity after
the final component is fully formed.
Key Points
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Fabric Types
Resin Types
Manufacturing Techniques
Curing Techniques
Sandwiches and Honeycombs
Joining of Composites
Pros and Cons of Composites
Where are Composites Used?
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Recreational boats
Cars
Airplanes and other aircrafts
Aerospace
High performance sporting goods
Appliances, tools, and machinery
Tanks and pipes
What is a Composite?
• First produced about 50 years ago
• A “Judicious” combination of two or
more materials that produces a
“Synergistic” effect
Judicious
• Implies that the components are
carefully selected to provide the
desired physical and chemical
characteristics
Synergistic
• The whole product is better than the sum
of its individual components
• Word coined by Buckminster Fuller
• Illustrated concept by using a rope as an
example
Composites are made up of a
fiber and a matrix
• Fiber can be short or long strands of
material
• Matrix is a the material that holds the
fibers together
• Natural composites – celery, corn stalks,
and sugar cane
• Manmade composite – reinforced
concrete
Composite Classification
• Matrix
– Material that surrounds the other components
• Fillers
– Randomly oriented equally dispersed particles
• Fiber Reinforcement
– Usually the main component in differing forms
Simple and Advanced
Composites
• Simple Composite (Reinforced plastic) –
Fiber laid in random directions or very
short
• Advance Composite – Long fibers are
laid in a given direction, long, and
continuous
Fiber orientation
• Unidirectional
• Biaxial (Cross-ply)
– Random orientation
• Laminates
– Cross layering of unidirectional composites
Composite System Categories
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Fiber – Resin
Fiber – Ceramic
Carbon – Metal
Metal – Concrete
Metal – Resin
Metal – Elastomer
Fiber – Elastomer
Wood – Resin
Typical Fabrics Used in
Composites
Glass
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Can be long and continuous or
short
Can use many different types ex:
Soda lime – easy and low cost
Fiberglass white color can be dyed
to any color
Kelvar
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Can be long and continuous
Same family as nylon
Distinctive yellow color
Graphite (carbon)
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Made by burning a material in the
absence of oxygen, other elements burn
off leaving carbon
Should be called carbon fiber
Always black
Strength to Weight
Why Chose Glass?
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Excellent thermal and impact resistance
High tensile strength
Good chemical resistance
Outstanding insulating properties
Lower cost
Glass Types
E-glass
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Low cost - $1 per pound
Used in 90% of glass reinforcement
Good electrical resistance
Used in aircraft radomes and
antennae and computer circuit boards
Good resistance to sodium carbonate
(base)
Good high temperature performance
C-glass
• Corrosion resistant
• Good resistance to hydrochloric and
sulfuric acid
• Poor high temperature performance
High strength glass
• $6 per pound
• S-glass or S2-glass(U.S.)
• R-glass (Europe)
• T-glass (Japan)
• Contains more silica oxide, aluminum
oxide, and magnesium oxide
• 40% to 70% stronger
• Originally used for military
applications (S2 for commercial)
• Good resistance to hydrochloric and
sulfuric acid
• Good resistance to sodium carbonate
(base)
• Good high temperature performance
Why Chose Graphite?
• Higher tensile strength and stiffness than
glass
• Used in high-tech applications where
product needs exceptional fiber properties
and customer is willing to pay premium
Why Chose Kevlar?
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Highest quality
High breaking strength
More impact resistant
Lightest weight
Highest tensile strength
Comparisons of Fibers & Steel
Tensile Strength
600,000
500,000
lb/in 2
400,000
300,000
200,000
100,000
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Fiber Types
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Comparisons of Fibers & Steel
Density
10
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gm/cm 3
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Fiber Types
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Hybrids
• Combination of different fibers
within a single matrix
Intraply
Interply
Hybrids
Interply Knitting
Selective Placement
Resins
• Must be compatible with fibers
• Two types
Thermoplastic
Thermosetting
Needs higher temperature processing
Crosslinks during curing
Remains plastic and can be reheated
and reshaped
Sets into final rigid form
Used less
High performance
Higher costs
Higher temperature performance
Better damage resistance
Higher compressive strength
High vibrational damping
Viscoelasticity
Used widely
Lower price tag
Ease of handling
Good balance of mechanical,
electrical, and chemical resistance
properties
Resins – Two Types
Thermoplastics
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ABS
PMMS
Fluorocarbon (Teflon)
Nylon
Polycarbonate
Polyphenylene sulfide
Polypropylene
Styrene
Vinyl
Vinylidines
Thermosetting
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Epoxy
Bakelite
Melamine
Polyesters
Urea-formaldehyde
Urethanes
Silicones
Manufacturing Techniques
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Hand layup or Hand-lay
Pre-preg
Filament winding
Pultrusion
Open Mold Processes
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Hand Lay-up
Spray-up
Tape-laying
Filament winding
Hand layup
• Oldest, Inexpensive, Little equipment required
• Repair technicians and backyard boat builders
use this technique with fiberglass
• Requires some skill to do
• Wasteful use of resin
• Product heavier compared to using other
techniques
• Good for one of a kind products or prototypes
Hand layup Method
1. A form is coated with resin using a
paintbrush, roller, swab, spatula or any
other method
2. Fabric is pressed into the resin
3. Another coat of resin is applied on top
Pre-preg Method
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Fabric saturated with resin
Excess squeezed out by rollers
Cured to B stage, material tacky
Can be stored a week to 10 days if not used
right away. Refrigeration lengthens shelf life
5. Can be wrapped around a mandrel, cut by
computer controlled machines or laid up on
forms by robots
6. Must be put under pressure to finish curing
Filament Winding Method
• Good for convex shapes
having no indentations
• Individual fibers are drawn
through the resin and
wrapped around a mandrel
• When complete pressure
cured, mandrel removed
• Good method for aircraft
nose cones, radar domes
and missile nose cones and
bodies
Pultrusion Method
• Good method for selective placement composites
• A bundle of arranged fibers are drawn through a resin
bath
• Then pulled through a selected shape heated die
• Cured and cut to size
• Good method to create channels, flange beams, Tbars, and other shapes in very long lengths
Pultrusion
Curing Techniques
• Pressure forms
• Vacuum bagging
• Autoclaving
Pressure Form Method
• Uses a heated
internal and external
mold
• Can be used in mass
production, but
requires expensive
equipment
Vacuum Bagging Method
• Simple and cheapest method
• Used after hand layup or pre-preg of
material
• Piece is placed in a polyethylene, rubber,
or airtight flexible bag
• Vacuum pull in the bag exerts equal
pressure approximately 12 lb/in2
• Part or entire bag is heated to cure
Autoclaving Method
• Used when parts require more than one
atmosphere of pressure
• An oven that can be sealed and pressure
is then applied by air or other gasses
Other Composite Forms
Sandwiches
• Styrofoam, syntactic foam, or polyurethane
foam wrapped in fiberglass, Kevlar, or
graphite fibers and fused together
• Balsa wood could be used as a core to make
sailboats
• Recent developments using ceramic cores for
heat resistance
Other Composite Forms
Honeycombs
• Honeycombed aluminum, Nomex,
fiberglass, graphite, or other material
wrapped and bonded to composite
materials
• Used in helicopter blades, truck and
aircraft bodies, and some parts of
aircraft wings and tail surfaces
Joining Composites
• Joined in conventional methods by
threads, pins, rivets, and other mechanical
methods
• Thermoplastic polymers joined by fusion
welding
• Chemical joining
• Adhesives
Composites vs. Traditional
Materials
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Pros
Lighter
Stronger
No fatigue failure
No corroding
Hard to break
Complicated shapes
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Cons
Delaminate
Blisters
Fabric cutting difficult
Material and curing
costs high
Environmental Concerns
Reduction of styrene emissions
• Exposure limited to 50 parts per
million (OSHA)
• Hard to meet standards and
costly
• Achieved by reducing styrene,
better transferring to molds,
curing in closed systems
Development of biodegradable
reinforced plastics
• Filling up landfills with computer
and car parts, packaging, etc.
• Create matrices from soybean
protein and use plant-based
fibers such as ramie, pineapple
leaves and banana stems
• Could be used in car and train
interiors, computers and as
packaging materials
• Low cost (when acceptance
increases), biodegradable and
renewable on a yearly basis
Websites
• www.composites-one.com
• www.msu.edu/~namaact/productinfo.htm