Transcript Slide 1

Composites. An overview
For CME/MSE 404G
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cme/mse 404g composite
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Outline
• Composite examples
• Fiber-reinforced
composites
• Matrices and fibers
• Effects of fiber
orientation
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• Multiple lamellae
structures
• Fiber/matrix wetting
• Composites
manufacturing
• Typical composite
design challenges
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Composite examples.
Properties, performance, processing, structure
Composite push rod
Tires
Brake shoes
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Composite Push Rod For Automobiles
•Properties
Collin. MSE 556. Spring, 2006
High compressive and tensile strength along the
axial direction; (secondary) stiff with respect to
torsion, bending and shear; temperature
resistance; chemical resistance to lubricants and
fuel gases
•Structure
Composite push rods are lighter
weight replacements for metallic
push rods in use between a cam
shaft and a valve rocker in internal
combustion engines. These
composite push rods are
constructed of a bar that is made of
carbon fiber. These composite push,
bars generally have flat ends to
which rounded metal end fittings are
bonded, usually by some type of
epoxy or adhesive. The composite
push rod then attaches to the cam
shaft and valve rocker via these
rounded metal end fittings.
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•Performance
Failure mechanisms: overloading
(tensile/compressive), torsion, off axis loading,
fatigue, crack growth/delamination less of a
concern
•Processing
In order to construct the composite push rod, the bar is first constructed
and then the ends are bonded. The bar is constructed of a plurality of
layers of sheets of epoxy impregnated, longitudinally oriented fiber
material that are wrapped around a removable mandrel. The sheets of
longitudinally oriented fiber material form the inner portion of the push
bar and a single outside sheet of epoxy impregnated, woven fiber
material that is wrapped around the sheets of longitudinally oriented fiber
material forms the outside portion of the bar. The sheets of fiber material
are comprised on a fiber, such as carbon, Kevlar, or glass, and the fiber
material is resin impregnated with a thermosetting, high temperature,
toughened epoxy. Once all of the layers of fiber material are wrapped
together, they are heated and compressed to thermo-set the layers into a
single composite bar. The mandrel is then removed, leaving a central
opening in the bar where the mandrel was located.
The ends of the composite bar are then cut to the proper shape and the
mating surfaces of the metal end fittings are bonded to the ends of the
composite bar via epoxy, thereby completing construction of the
composite push rod.
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Performance
Tires
Optimal performance is achieved by proper use and
maintenance. Understanding the labeling or sidewall
markings is key. Example:
P215/65R15 89H
P: passenger, vs. LT that has higher ply ratings
215: width
65: aspect ratio
R: radial, vs. belted construction or diagonal construction
15: diameter of wheel
89: load index--indicates the max weight each tire can
support
H: speed rating—measurement of top safe speed the tire
can carry a load under specified conditions. (worst to best:
Q,S,T,U,H,V,Z,W,Y) *a higher rated tire will give better
traction and improved steering response at 50 mph.
Also consider:
-Max. cold inflation (in psi) see images below!**very
important
-Load limit (redundant to load index)
-treadware grading--how long the tread will last
-traction grading—indicates tires ability to stop in a straight
line on wet pavement
-temp grading—min speed a tire will not fail at high temp.
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Processing
1. The process begins with the mixing of basic rubbers with process oils, carbon
black, pigments, antioxidants, accelerators and other additives, each of which
contributes certain properties to the compound. These ingredients are mixed in
giant blenders called Banbury machines operating under tremendous heat and
pressure. They blend the many ingredients together into a hot, black gummy
compound that will be milled again and again.
2. This compound is fed into mills which feed the rubber between massive pairs of
rollers,feeding, mixing and blending to prepare the different compounds for the
feed mills, where they are slit into strips and carried by conveyor belts to become
sidewalls, treads or other parts of the tire.
Still another kind of rubber coats the fabric that will be used to make up the tire's
body. Many kinds of fabrics are used: polyester, rayon or nylon.
3. Another component, shaped like a hoop, is called a bead. It has high-tensile
steel wire forming its backbone, which will fit against the vehicle's wheel rim. The
strands are aligned into a ribbon coated with rubber for adhesion, then wound into
loops that are then wrapped together to secure them until they are assembled with
the rest of the tire.
Radial tires are built on one or two tire machines. The tire starts with a double
layer of synthetic gum rubber called an innerliner that will seal in air and make the
tire tubeless.
4. Next come two layers of ply fabric, the cords. Two strips called apexes stiffen
the area just above the bead. Next, a pair of chafer strips is added, so called
because they resist chafing from the wheel rim when mounted on a car.
The tire building machine pre-shapes radial tires into a form very close to their
final dimension to make sure the many components are in proper position before
the tire goes into the mold.
5. Now the tire builder adds the steel belts that resist punctures and hold the tread
firmly against the road. The tread is the last part to go on the tire. After automatic
rollers press all the parts firmly together, the radial tire, now called a green tire, is
ready for inspection and curing.
6. The curing press is where tires get their final shape and tread pattern. Hot
molds like giant waffle irons shape and vulcanize the tire. The molds are engraved
with the tread pattern, the sidewall markings of the manufacturer and those
required by law.
Tires are cured at over 300 degrees for 12 to 25 minutes, depending on their size.
As the press swings open, the tires are popped from their molds onto a long
conveyor that carries them to final finish and inspection.
**This is traditional technique by goodyear, new automated processes are used by
404g
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pirelli. composite
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References: 1010tires.com, goodyeartires.com, us.pirelli.com
Properties
Structure
RUBBER PERCENT BY WEIGHT IN A
NEW RADIAL PASSENGER TIRE
Typical phsyical properties of a universal tire
Physical Properties
Universal
Hardness (Shore A,D)
67A
Compression Modulus
(psi)
900
Deflection @ 100psi
11.56
Deflection @ 300psi
26.71
Tear Strength (pli)
Tensile Strength (psi)
Weight % for Passenger Tire
Natural
14 %
rubber
Synthetic
rubber
27%
Carbon black
28%
Steel
14 - 15%
249
2,950
Ultimate Elongation (%)
690
300% Modulus (psi)
990
Bayshore Rebound (%)
38
Compression Set (%)
13
Fabric, fillers,
accelerators,a
ntiozonants,
etc.
TREAD
BASE
21.9%
BEAD APEX
5.0%
BEAD INSULATION
1.2%
FABRIC INSULATION
INNERLINER
www.superiortire.com
11.8%
9.5%
12.4%
3.9
%
UNDERCUSHION
Hardness (Shore A,D) - measures resistance to indentation. A "soft" elastomer & D for
"harder" materials.
Compression Modulus (psi) - force required to achieve a specific deflection, typically
50% deflection, predicts a material's rigidity or toughness.
Tear Strength (pli) - measures the resistance to growth of a nick or cut when tension is
applied to a test specimen, critical in predicting work life
Tensile Strength (psi) - ultimate strength of a material when enough force is applied to
cause it to break, with elongation and modulus, tensile can predict a material's toughness.
Ultimate Elongation (%) - percent of the original length of the sample measured at point
of rupture.
300% Modulus (psi) - stress required to produce 300% elongation.
Bayshore Rebound (%) - resilience of a material. ratio of returned energy to impressed
energy. predicts rolling resistance.
Compression Set (%) - measures the deformation remaining in an elastomer after
removal
of the deforming force. In combination withcme/mse
rebound, set
values
predict an
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elastomer's success in a dynamic application.
overview
http://www.p2pays.org/ref/11/10504/html/intro/tire.htm
1.7%
SIDEWALL
INSULATION OF STEEL CORD
16 - 17%
32.6%
100.0%
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Brake Shoes
Properties
Density (gm/cc) 1.80 - 2.00
Rockwell Hardness (HRL) 75 – 100
Busting Strength (rpm)> 12,000Max.
Continuous Operating Temp.200°CMax.
Transient Operating Temp. 300°C
Structure
Performance
*Riveted linings provide superior performance, but good
quality bonded linings are perfectly adequate.
*Organic and non-metallic asbestos compound brakes are
quiet, easy on rotors and provide good feel. But this comes
at the expense of high temperature operation.
*In most cases, these linings will wear somewhat faster than
metallic compound pads, so you will usually replace them
more often. But, when using these pads, rotors tend to last
longer.
*The higher the metallic content, the better the friction
material will resist heat.
Processing
The pad or shoe is composed of a metal backing plate and a
Casting metal backing plate
friction lining.
Electric Infrared ovens used
Friction materials vary between manufacturers and type of
Shoe Prep
pad: asbestos, organic, semi-metallic, metallic.
Washing, Delining ,Shot Blasting, return of shoes to OE
Exotic materials are also used in brake linings, among which
specs, relining, riveting
are Kevlar® and carbon compounds.
Phenolic polymer matrix composites are used as brake
pad/shoe materials. As a new disc/drum materials,
aluminimum metal matrix composites (Al MMCs) are
attractive for their lightweight (three times lighter than cast
iron) properties, higher thermal conductivity, specific heat,
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superior
mechanical properties and higher wear resistance
over cast iron.
overview
Fiber-reinforced composites
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Applications. Fiber-reinforced
composites
• Aircraft and military – F14 horizontal
stabilizers, 1969.
• Space – boron fiber-reinforced aluminum
tubes, Kevlar/epoxy pressure vessels
• Automotive – body (Class A finish,
polyurethanes), chassis (Corvette rear leaf
spring), engine
• Sporting goods –weight redution
• Marine – boat hulls, decks, bulkheads
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Fiber alignment
•
•
•
•
Unidirectional, continuous
Bidirectional, continuous
Unidirectional, discontinuous
Random, discontinuous
Fibers + matrix + coupling agents + fillers
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lamina
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Matrix and fiber properties
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Resin Properties
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Common commercial matrices
• Thermosets: epoxies, polyester, vinyl
ester, phenolics, polyimides
• Thermoplastics: nylons, linear polyesters,
polycarbonate, polyacetals, polyamideimide, PEEK, PSul, PPS, PEI
• Metallic – Al alloys, Ti alloys, Mg alloys,
copper alloys, nickel alloys, SS
• Ceramic – aluminum oxide, carbon silicon
carbide, silicon nitride
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Fiber properties
•
•
•
•
•
•
Specific gravity
Tensile strength, modulus
Compressive strength, modulus
Fatigue strength
Electrical, thermal conductivity
cost
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Fiber Properties
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Effect of fiber diameter on strength
Fiber that are formed by spinning
processes usually have
increased strength at smaller
diameters due to the high
orientation that occurs during
processing.
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Common commercial fibers
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•
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•
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Glass
Graphite
Kevlar 49
PE (Spectra)
Boron
Ceramic – SiC, Al2O3
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Effects of fiber orientation
Continous, aligned fibers.
Morphology and mechanical
properties
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Representative Element of an
Aligned-Fiber Bundle
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(a) Micrograph of a carbon epoxy composite
(b) square packing array
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Stiffness of a unidirectional carbon epoxy
laminate as a function of test angle relative
to fiber direction
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Effect of average fiber volume Vf on the axial
permeability of an aligned-fiber bundle
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Fiber volume fraction (Vf)
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Viscosity change and cure cycle for graphite/epoxy
composite (Hercules AS4/3501-6)
In general, matrix viscosity
increases with temperature
until the polymer cures to
the gel state. Above this
temperature, local chain
motion is restrained by
crosslinks, and additional
curing for higher
crosslinking can require
long “post-cure” times.
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Fiber volume fraction Vf versus processing viscosity, µ.
common polymer matrix systems
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Multiple lamellae structures
Design issues
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Linear Fiber Structure [0/90/0]
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Top and side views of woven
(interlaced) fibers
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Combination fiber structure showing linear
fibers and interlacing through the thickness
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Illustration of idealized, linear 3D
fiber structures
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Stacking sequence of a (0/90±45)s
quasi-isotropic layup
Symmetric layups prevent
warping under
stress, thermal
expansion
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In-plane stiffnesses of various-ply geometries as a function
of test angle, relative to the on-axis stiffness of a
unidirectional laminate
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Relative modulus vs.
fiber volume fraction
Range of
obtainable
elastic moduli
for various
composites
normalized by
the fiber
modulus, Ef,
versus the
fiber volume
fraction
(configuration
indicated)
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Fiber/matrix wetting
Wetting of the fibers
by the matrix material
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Illustration of spontaneous wetting
(a) at t=t0 and (b) at t>t0
Matrix material is often added to fiber assemblies, and needs to wet the
fibers in order to prevent void formation.
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Surface Energies
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Resin infiltration of unidirectional glass fibers in
[0/90] layup showing the formation of voids
Resin has wicked into
several orthogonal
lamellae, forming voids
(bubbles). The slight
refractive index difference
between fiber and matrix
allows the fiber directions
to be observed.
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Composites processing
Hand lay-up,+/- molds, filament
winding, pultrusion, resin transfer
molding, vacuum forming
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Schematics of (a) hand layup and (b)
mechanically assisted hand layup
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Several bagged composite parts being rolled
into the autoclave for cure
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Schematic of the filament winding process
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Examples of unstable fiber paths in
the filament winding process
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Filament winding of a rocket motor tube
e.g., booster rocket
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Schematic of automatic tow
placement process showing seven
axes of motion
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Automatic fiber placement of the V-22 aft
fuselage section on the Cincinnati-Milacron
seven-axis CNC fiber placement machine
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Inside view of the fiber placed V-22 fuselage
section secured with stiffeners
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Schematic of the pultrusion process
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Examples of pultruded part cross
sections including airfoil shapes and
structural skins and stiffeners
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Examples of pultruded part cross
sections including airfoil shapes and
structural skins and stiffeners
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Schematic of the resin transfer modeling
process showing (a) fiber preform and (b)
resin injection into fiber preform
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The body panels for the Chrysler Viper are made
by resin transfer molding (RTM)
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Schematic of the double diaphram
forming process
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Double-diaphragm-formed parts produced from
graphite/epoxy prepregs and then cured (upper-curved Cchannel; lower-radio-controlled car chassis)
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Typical composite design
challenges
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Example of how microstructural details can lead to warping
or shape changes in the composite along with the solutions
for the problem
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Alternate assembly methods
illustrated for a curved C-channel
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