Introduction to Composites.
Case Study – Boeing 787
Introduction to composites
What is a composite Material ?
Two or more chemically distinct materials which when
combined have improved properties over the individual
Example: Wood, Bamboo, Bricks.
Composites are combinations of two materials in which
one of the material is called the reinforcing phase, is in
the form of fibers, sheets, or particles, and is embedded in
the other material called the matrix phase.
Composites – Polymer Matrix
Polymer matrix composites (PMC) and fiber reinforced plastics (FRP) are
referred to as Reinforced Plastics. Common fibers used are glass (GFRP),
graphite (CFRP), boron, and aramids (Kevlar). These fibers have high specific
strength (strength-to-weight ratio) and specific stiffness (stiffness-toweight ratio)
Matrix materials are usually thermoplastics or thermosets; polyester,
epoxy (80% of reinforced plastics), fluorocarbon, silicon, phenolic.
Composites – Metal Matrix
The metal matrix composites offer higher modulus of elasticity, ductility,
and resistance to elevated temperature than polymer matrix composites.
But, they are heavier and more difficult to process.
Composites – Ceramic Matrix
Ceramic matrix composites (CMC) are used in applications where
resistance to high temperature and corrosive environment is
desired. CMCs are strong and stiff but they lack toughness
Matrix materials are usually silicon carbide, silicon nitride and
aluminum oxide, and mullite (compound of aluminum, silicon and
oxygen). They retain their strength up to 3000 oF.
Fiber materials used commonly are carbon
and aluminum oxide.
Applications are in jet and automobile
engines, deep-see mining, cutting tools,
dies and pressure vessels.
Application of Composites
Swedish Navy, Stealth
Pedestrian bridge in
Denmark, 130 feet long
A Process wherein the
application of resin and
reinforcement is done by
hand onto a suitable mould
surface. The resulting
laminate is allowed to cure in
place without further
Glass fibers chopped up
Resin, catalyst, & fibers sprayed onto a mold
Cures at ambient temperature and atmospheric pressure
Vacuum Bag Molding
Two-sided mold set.
Shapes both surfaces of the panel.
Lower side is a rigid mold
Upper side is a flexible membrane or vacuum bag
Bag made of silicone material or an extruded polymer film.
Performed at either ambient or elevated temperature.
Ambient atmospheric pressure acts upon the vacuum bag.
Most economical way uses venturi vacuum and air
compressor or a vacuum pump.
Two-sided mold set
Lower Side rigid mold
Upper Side flexible membrane made from silicone or an
extruded polymer film
Reinforcement materials can be placed manually or robotically
Include continuous fiber forms fashioned into textile
Use of autoclave pressure vessel
process generally performed at both elevated pressure and
elevated pressure facilitates a high fiber volume fraction
Elevated pressure yields low void content for maximum
Uses elevated pressure and temperature to consolidate plastic and fibers
into a solid structure
Various range of sizes
Small Laboratory Prototype models
Aircraft and Large Application models
Used for high-performance parts with the
highest strength-to-weight ratios
VARTM and RTM
Vacuum Assisted Resin Transfer Molding
Sometimes a pump used to remove any air within the system
Resins permeate through the material from the top displacing air
Uses low viscosity catalyzed resins injected into the piece
Cures with low temperature and low pressure
Benefits the of the 787 (aka. “Dreamliner”)
I. Light weighta. Fuel efficient
b. Longer range than comparable aircraft
II. Reduced maintenance costs
a. $30-40 million in savings
i. High reduction in fatigue
ii. Highly corrosion resistant
III. Increased passenger comfort
a. Increase in cabin pressure
b. Increased humidity
i. Result of high corrosion resistance
c. Bigger windows due to increased strength
d. Less noise
i. Front engine cowl intake is made of a
single piece of composite, reducing drag
IV. Decreased assembly time
a. Parts arrive from suppliers as net-shape
b. Components are pre-installed in parts at
Cost- Benefit Analysis of the Boeing 787
I. Boeing estimates that 787 will consume $5 million less
in fuel on a comparable route than 767
a. Savings = Price of plane
II. Potentially longer life
a. Not proven yet, but likely due to the
high reduction in corrosion and fatigue
Changes Boeing Has Made in Order to Create a
I. Composites are made elsewhere.
a. Attached in the factory using titanium
hardware and adding carbon sheets where
II. Safety equipment
a. Revamped to provide protection from
II. New machines and equipment
a. Alignment machines to assemble tubes
i. Needed in order to attach fuselage
due to low flexibility of fuselage
Automated Tape Laying machine- Used
to the layup of the flight deck floor
Fuselage Unloader- Used to unload fuselage
sections from Dreamlifter
Some difficulties and problems Boeing has encountered
during this project, and how have they been overcome
I. Estimating weights of composite parts very difficult
a. Current plane is overweight
i. Redesign parts to conform to specs
II. Problems detecting and repairing damage
a. Composites pose a great challenge to finding
flaws and cracks
III. Value of components very high preceding machining
IV. How to recycle
a. One time material use?
Application of Composites in
20% more fuel efficiency
and 35,000 lbs. lighter
Disadvantages of Composites
Composites are heterogeneous
properties in composites vary from point to point in the material. Most
engineering structural materials are homogeneous.
Composites are highly anisotropic
The strength in composites vary as the direction along which we measure
changes (most engineering structural materials are isotropic). As a result, all
other properties such as, stiffness, thermal expansion, thermal and electrical
conductivity and creep resistance are also anisotropic. The relationship
between stress and strain (force and deformation) is much more complicated
than in isotropic materials.
The experience and intuition gained over the years about the behavior of metallic
materials does not apply to composite materials.
Disadvantages of Composites
Composites materials are difficult to inspect with conventional ultrasonic, eddy
current and visual NDI methods such as radiography.
American Airlines Flight 587, broke apart over New
York on Nov. 12, 2001 (265 people died). Airbus
A300’s 27-foot-high tail fin tore off. Much of the
tail fin, including the so-called tongues that fit in
grooves on the fuselage and connect the tail to the
jet, were made of a graphite composite. The plane
crashed because of damage at the base of the tail
that had gone undetected despite routine
nondestructive testing and visual inspections.
Disadvantages of Composites
In November 1999, America’s Cup boat “Young America” broke in two due to
debonding face/core in the sandwich structure.
Future uses of structural composites:
Today it is easy to be optimistic about the future use
of composite materials in the automotive industry.
Substitution of metals with composites not unavoidable and
Composite material applications will increase, but
they will never completely replace metals
Composite materials have enormous potential
Industry will need to demonstrate advantages for each
application and compete with advocates of metals
Designers should seek to work with both materials
exploiting best characteristics for a given application
Nanoparticulates (filler) introduced into a macroscopic sample material
Percentage by weight (mass fraction) of the nanoparticulates can remain very
on the order of 0.5% to 5%
Nanocomposite may exhibit enhanced properties
electrical and thermal conductivity
…Or nanoparticles can impart new physical properties and behaviors to
matrix (genuine nanocomposites or hybrids)
Nanocomposite: Under a
Continuous Carbon Nanotube Reinforced Composites
3300% improvement in longitudinal modulus under
up to 2100% improvement in damping capability
composites with a random distribution of nanotubes of same
length and similar filler fraction provide 3x less effective
reinforcement in composites.
Cyclics CBT resin nano-composite structure produces
properties not previously possible with traditional
Thermoplastic with near water viscosity
Headquarted in Schenectady
Nanocomposites in BioMed
Bio-mimicking artificial muscles or skins
Soft tissue-like material can be made into an
Don’t have to add mechanical motors
Composite of PMMA and hydroxyapatite w/ MWCNT
can be used as next-gen bone cement
Biosensors using Sol-Gel technology