Composites have actually been in use for thousands of years.
Adobe bricks were made using a composite of mud and straw. It is
the combination of the physical properties of each material that
gives the composite material many of its physical characteristics.
Todays advanced composites, like carbon fiber, bring together
combined properties weve come to know lightweight, strong, durable
and heat-resistant. Today, the benefits of components and products
designed and produced in composite materials instead of metals,
such as aluminum and steel are well recognized by many industries.
Some of the advantages include: Composites Defined, Section 1
Slide 8
Composite materials in transport airplane components are being
used for decades. Prior to the mid-1980s, airplane manufacturers
used composite materials in transport category airplanes in
secondary structures (e.g., wing edges) and control surfaces. In
1988, Airbus introduced the A320, the first airplane in production
with an all-composite tail section and, in 1995, the Boeing Company
introduced the Boeing 777, also with a composite tail section.
Composite materials used in commercial airplanes typically are
produced by combining layers of carbon or glass fibers with epoxy.
In recent years, manufacturers have expanded the use of composites
to the fuselage and wings because these materials are typically
lighter and more resistant to corrosion than are the metallic
materials that have traditionally been used in airplanes. History,
Section 1
Slide 9
The rapid development and use of composite materials beginning
in the 1940s had three main driving forces. Military vehicles, such
as airplanes, helicopters, and rockets, placed a premium on
high-strength, light-weight materials. While the metallic
components that had been used up to that point certainly did the
job in terms of mechanical properties, the heavy weight of such
components was prohibitive. The higher the weight of the plane or
helicopter itself, the less cargo its engines could carry. Polymer
industries were quickly growing and tried to expland the market of
plastics to a variety of applications. The emergence of new,
light-weight polymers from development laboratories offered a
possible solution for a variety of uses, provided something could
be done to increase the mechanical properties of plastics. The
extremely high theoretical strength of certain materials, such as
glass fibers, was being discovered. The question was how to use
these potentially high-strength materials to solve the problems
posed by the military's demands.
Slide 10
Composite Wings -The Wright Flyer was constructed of muslin
fabric stretched over a spruce frame. History, Section 1
Slide 11
What Is a Composite Material? Two or more materials combined to
perform some useful purpose Exhibits the best properties of the
individual materials and includes additional qualities that the
individual materials do not exhibit alone
Light Weight - Composites are light in weight, compared to most
woods and metals. Their lightness is important in automobiles and
aircraft, for example, where less weight means better fuel
efficiency (more miles to the gallon). People who design airplanes
are greatly concerned with weight, since reducing a crafts weight
reduces the amount of fuel it needs and increases the speeds it can
reach. Some modern airplanes are built with more composites than
metal including the new Boeing 787, Dreamliner. High Strength -
Composites can be designed to be far stronger than aluminum or
steel. Metals are equally strong in all directions. But composites
can be engineered and designed to be strong in a specific
direction. Corrosion Resistance - Composites resist damage from the
weather and from harsh chemicals that can eat away at other
materials. Composites are good choices where chemicals are handled
or stored. Outdoors, they stand up to severe weather and wide
changes in temperature.
Slide 14
Introduction to composites, Section 1 Strength Related to
Weight - Strength-to-weight ratio is a materials strength in
relation to how much it weighs. Some materials are very strong and
heavy, such as steel. Other materials can be strong and light, such
as bamboo poles. Composite materials can be designed to be both
strong and light. This property is why composites are used to build
airplanes which need a very high strength material at the lowest
possible weight. A composite can be made to resist bending in one
direction, for example. When something is built with metal, and
greater strength is needed in one direction, the material usually
must be made thicker, which adds weight. Composites can be strong
without being heavy. Composites have the highest strength-to-weight
ratios in structures today. Corrosion Resistance - Composites
resist damage from the weather and from harsh chemicals that can
eat away at other materials. Composites are good choices where
chemicals are handled or stored. Outdoors, they stand up to severe
weather and wide changes in temperature. Part Consolidation - A
single piece made of composite materials can replace an entire
assembly of metal parts. Reducing the number of parts in a machine
or a structure saves time and cuts down on the maintenance needed
over the life of the item.
Slide 15
Introduction to composites High-Impact Strength - Composites
can be made to absorb impactsthe sudden force of a bullet, for
instance, or the blast from an explosion. Because of this property,
composites are used in bulletproof vests and panels, and to shield
airplanes, buildings, and military vehicles from explosions. Design
Flexibility - Composites can be molded into complicated shapes more
easily than most other materials. This gives designers the freedom
to create almost any shape or form. Most recreational boats today,
for example, are built from fiberglass composites because these
materials can easily be molded into complex shapes, which improve
boat design while lowering costs. The surface of composites can
also be molded to mimic any surface finish or texture, from smooth
to pebbly. Dimensional Stability - Composites retain their shape
and size when they are hot or cool, wet or dry. Wood, on the other
hand, swells and shrinks as the humidity changes. Composites can be
a better choice in situations demanding tight fits that do not
vary. They are used in aircraft wings, for example, so that the
wing shape and size do not change as the plane gains or loses
altitude. Nonconductive - Composites are nonconductive, meaning
they do not conduct electricity. This property makes them suitable
for such items as electrical utility poles and the circuit boards
in electronics. If electrical conductivity is needed, it is
possible to make some composites conductive.
Slide 16
Introduction to composites, Section 1 Nonmagnetic - Composites
contain no metals; therefore, they are not magnetic. They can be
used around sensitive electronic equipment. The lack of magnetic
interference allows large magnets used in MRI (magnetic resonance
imaging) equipment to perform better. Composites are used in both
the equipment housing and table. In addition, the construction of
the room uses composites rebar to reinforced the concrete walls and
floors in the hospital. Radar Transparent - Radar signals pass
right through composites, a property that makes composites ideal
materials for use anywhere radar equipment is operating, whether on
the ground or in the air. Composites play a key role in stealth
aircraft, such as the U.S. Air Forces B-2 stealth bomber, which is
nearly invisible to radar. Low Thermal Conductivity - Composites
are good insulatorsthey do not easily conduct heat or cold. They
are used in buildings for doors, panels, and windows where extra
protection is needed from severe weather. Durable - Structures made
of composites have a long life and need little maintenance. We do
not know how long composites last, because we have not come to the
end of the life of many original composites. Many composites have
been in service for half a century.
Slide 17
Design flexibility, including parts consolidation Molded in
tight tolerances, often eliminating machining operations High
strength to weight performance Retention of properties Corrosion
resistant in hostile environments and underload Outstanding
dielectric strength and comparative track resistance Good surface
appearance with molded-in color and texture Net-Shape Molded vs.
Machined Metal, Section 1
Slide 18
Low Cost Per Cubic Inch Dimensional Stability Corrosion
Resistance Electrical Performance U.L. Recognition High Strength
Rigid and Strong Design Flexibility Low Coefficient of Thermal
Expansion Dimensional Accuracy FDA Compliance Low Smoke Density -
Low Flame Spread Index Stain Resistance Microwave Transmissivity
Low Resonance and Sound Dampening Fundamentals of Composites,
Section 1
Slide 19
Most materials are isotropic Meaning that their properties are
the same in all directions Metals, polymers, ceramics Composites
are anisotropic Meaning that their properties are different in
different directions Wood, plywood Fundamentals of Composites,
Section 1
Slide 20
Slide 21
Composite Material Types, Section 1
Slide 22
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-to-weight ratio) Matrix materials
are usually thermoplastics or thermosets; polyester, epoxy (80% of
reinforced plastics), fluorocarbon, silicon, phenolic Composite
Material Types, Section 1
Slide 23
Low material cost per cubic inch Formulating latitude to meet
specific requirements and cost parameters with good speed to market
Dimensional accuracy and stability, combined with good property
retention, over a broad range of temperatures Design flexibility in
molding from thin to thick sections Non-melting, flame retardant
and low smoke density Solvent resistant Why Thermoset Composites,
Section 1
Slide 24
Composites vs. Metal, Section 1
Slide 25
The lowest properties for each material are associated with
simple manufacturing processes and material forms (e.g. spray
lay-up glass fibre), and the higher properties are associated with
higher technology manufacture (e.g. autoclave moulding of
unidirectional glass fibre), the aerospace industry Composites have
a higher specific strength than many other materials. A distinct
advantage of composites over other materials is the ability to use
many combinations of resins and reinforcements, and therefore
custom tailor the mechanical and physical properties of a
structure. Composites vs. Metal, Section 1
Slide 26
Net-Shape Molded vs. Machined Metal, Section 1
Slide 27
The use of composites and other advanced materials in aircraft
design and manufacturing, resulting in an industry-leading product
line of economical and environmentally-friendly jetliners for
Boeing it is the 787 and AIRBUS it is AWB 350 Composite materials
maximize weight reduction as they typically are 20 per cent lighter
than aluminum and are known to be more reliable than other
traditional metallic materials, leading to reduced aircraft
maintenance costs, and a lower number of inspections during
service. Additional benefits of composite technologies include
added strength and superior durability for a longer lifespan. To
fully leverage these benefits, aircraft designers are continuously
developing technologies to improve the speed of composite
manufacturing, as it is more complicated than with traditional
metallics. In addition, the company regularly seeks new-generation
applications for composite materials during the development
processes and beyond. Composites vs. Metal, Section 1
Slide 28
Damage categories : According to FAA, damage is categorized
according to its severity as follows. Category 1 Allowable damage
that may go undetected by scheduled or direct field inspection,
allowable manufacturing defects; damage below Allowable Damage
Limit (ADL), e.g. barely visible impact damage (BVID). Category 2
Damage detected by scheduled or directed field inspection at
specified intervals, e.g. exterior skin damage, interior stringer
blade damage. Category 3 Obvious damage detected within a few
flights, e.g. accidental damage to lower fuselage or lost bonded
repair patch. Category 4 Discrete source damage immediately known
by pilot to limit flight maneuvers, e.g. rotor disk cut through
fuselage or severe rudder lightning damage. Category 5 Severe
damage created by anomalous ground or flight events. Such damage
represents damage/manufacturing events that are outside of design
considerations. It does not drive stress analysis, it rather
relates to a feedback lop from maintenance/operations to the
authorities. Analogous to an automobile accident special directed
inspections are needed for category 5 damage. Damage of categories
1 to 4 has to be taken into account during aircraft design. For
damages of category 2 to 5 repair scenarios are required. Damage
Assessment and Repair Inspection, Section 1
Slide 29
Who is responsible for the safety of composite structure? The
responsibility of the safety of an airplane, and subsequently of
the safety of composite structure, is shared between three parties:
The Airworthiness Authorities (e.g: FAA in US, EASA in Europe) are
responsible for setting the certification standard and certifying
that the airplane manufacturers and parts suppliers meet their
standards. They also conduct periodic inspections of manufacturing
facilities to ensure continued compliance with regulations, and
oversee airplane repair facilities to ensure they follow the proper
maintenance and training procedures. The airplane manufacturers are
responsible for showing compliance with those regulations and
building safe airplanes. They are also developing airplane
maintenance programs and repair manuals and provide requested
on-site technical assistance. The operators are responsible for
operating airplane according to Airworthiness Authority rules and
the manufacturer approved manuals. This includes performing
adequate maintenance action when appropriate. Airplane operators
also help maintaining the airworthiness of their airplane fleets by
tracking their airplanes service history and reporting relevant
repair and incident data to Authorities and the manufacturers.
Damage Assessment and Repair Inspection, Section 1
Slide 30
Disadvantage of Composites, Section 1 In November 1999,
Americas Cup boat Young America broke in two due to debonding
face/core in the sandwich structure. American Airlines Flight 587,
broke apart over New York on Nov. 12, 2001 (265 people died).
Airbus A300s 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