Intro to Composites 110
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Class Outline
Class Outline
Objectives
Engineering Materials
What Is a Composite?
What Is a Matrix?
Thermoset and Thermoplastic Matrices
What Is a Reinforcement?
Reinforcement Forms
Product Fabrication
Composite Processing Methods
Pros and Cons of Composites
Composite Applications
Summary
Lesson: 1/12
Objectives
l Describe the different types of engineering materials used in manufacturing.
l Define a composite.
l Define a matrix.
l Distinguish between thermoset and thermoplastic matrices.
l Define a reinforcement.
l Describe reinforcement forms.
l Describe how composites are used in product fabrication.
l Distinguish between different composite processing methods.
l List the pros and cons of composites.
l Describe composite applications.
Figure 1. Bulk molding compound is available in
a putty-like log or in sticky fibers.
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Lesson: 1/12
Objectives
l Describe the different types of engineering materials used in manufacturing.
l Define a composite.
l Define a matrix.
l Distinguish between thermoset and thermoplastic matrices.
l Define a reinforcement.
l Describe reinforcement forms.
l Describe how composites are used in product fabrication.
l Distinguish between different composite processing methods.
l List the pros and cons of composites.
l Describe composite applications.
Figure 1. Bulk molding compound is available in
a putty-like log or in sticky fibers.
Figure 2. Spray-up molding is an open mold
method of processing composites.
Lesson: 2/12
Engineering Materials
In manufacturing, a wide variety of materials can be used to construct an array of different
products. Choosing a material depends on the properties required for the finished product, such as
strength, stiffness, density, and service temperature. In general, engineering materials can be
divided into four groups: metals, plastics, ceramics, and composites.
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Metals are one of the oldest materials used in industry. They provide a high level of strength,
stiffness, conductivity, and thermal stability. However, they are also heavy compared to other
materials. Iron, aluminum, and copper are some of the most commonly used metals, but most
Lesson: 2/12
Engineering Materials
In manufacturing, a wide variety of materials can be used to construct an array of different
products. Choosing a material depends on the properties required for the finished product, such as
strength, stiffness, density, and service temperature. In general, engineering materials can be
divided into four groups: metals, plastics, ceramics, and composites.
Metals are one of the oldest materials used in industry. They provide a high level of strength,
stiffness, conductivity, and thermal stability. However, they are also heavy compared to other
materials. Iron, aluminum, and copper are some of the most commonly used metals, but most
manufacturing applications today use metal alloys rather than pure metals. The cookware in Figure
1 is made from steel and copper.
Plastics are the most commonly used engineering material. Plastics, like the containers in Figure 2,
are lightweight, easy to process, and resistant to corrosion. However, plastics have poor thermal
stability and can lose their structural integrity in temperatures above 212° F (100° C).
Figure 1. Metals provide a high level of
strength, stiffness, conductivity, and thermal
stability.
Ceramics, shown in Figure 3, are created by exposing certain materials to extremely high
temperatures, and then allowing them to cool. Ceramics have a high level of rigidity and resistance
to heat. Most ceramics can withstand temperatures that are well above 1,800° F (982° C). However, ceramics can be brittle and may fracture from stress or impact.
Composites are some of the newest materials being used in manufacturing. A composite is simply
two or more materials that have been combined to create a lightweight material of superior
strength, stiffness, and durability. A composite material is shown in Figure 4.
In this class, you will learn about some of the basic materials used to make composites. You will
also learn how composites are processed, as well as common applications of composites.
Figure 2. Plastics are lightweight, easy to
process, and resistant to corrosion.
Figure 3. Ceramics have a high level of rigidity
and resistance to heat.
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and resistance to heat.
Figure 4. Composites are some of the newest
materials being used in manufacturing.
Lesson: 3/12
What Is a Composite?
A composite is made by combining two or more materials, such as a binding ingredient, known as
a matrix, with small filaments of solid material called reinforcements. Examples of composites
include fiber reinforced plastics (FRP), regular reinforced concrete, steel reinforced concrete, particle
filled plastics, rubber reinforced plastics, wood laminates, ceramic mixtures, and certain alloys.
Composites have become increasingly popular throughout different industries because they can
combine the advantages of different engineering materials. Composites have the strength of metal,
the light weight of plastic, and the rigidity of ceramics. In addition, a great variety of raw materials
can be used to make a composite, including metals, alloys, plastics, minerals, and wood. This
diversity of material allows the properties of the composite to be customized to meet the specific
requirements of an application. For example, you would use a different type of composite to create
a highly ductile part than you would use to create a highly rigid part.
Many of the items you use in your daily life are made, at least in part, of composites. The panel in
your car door, the fiberglass tub or shower in your home, and various sporting goods such as golf
clubs, fishing poles, and snowboards are made of composites. The products shown in Figures 1
and 2 are made from composites.
Figure 1. This molded sink is made from
composites.
Figure 2. These golf club shafts are made from
composites.
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Lesson: 3/12
What Is a Composite?
A composite is made by combining two or more materials, such as a binding ingredient, known as
a matrix, with small filaments of solid material called reinforcements. Examples of composites
include fiber reinforced plastics (FRP), regular reinforced concrete, steel reinforced concrete, particle
filled plastics, rubber reinforced plastics, wood laminates, ceramic mixtures, and certain alloys.
Composites have become increasingly popular throughout different industries because they can
combine the advantages of different engineering materials. Composites have the strength of metal,
the light weight of plastic, and the rigidity of ceramics. In addition, a great variety of raw materials
can be used to make a composite, including metals, alloys, plastics, minerals, and wood. This
diversity of material allows the properties of the composite to be customized to meet the specific
requirements of an application. For example, you would use a different type of composite to create
a highly ductile part than you would use to create a highly rigid part.
Many of the items you use in your daily life are made, at least in part, of composites. The panel in
your car door, the fiberglass tub or shower in your home, and various sporting goods such as golf
clubs, fishing poles, and snowboards are made of composites. The products shown in Figures 1
and 2 are made from composites.
Figure 1. This molded sink is made from
composites.
Figure 2. These golf club shafts are made from
composites.
Lesson: 4/12
What Is a Matrix?
In a composite, the matrix is the material that binds reinforcing fibers together. Typically the
matrix
starts
off Tooling
as a viscous
hardens to give shape to the composite part and to
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U, LLC. material
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protect the fibers from damage. The matrix also transfers the load to the fibers. In essence, the
matrix enhances the support provided by the fibers. Individual filaments, or fiber bundles, provide
little support by themselves. When bound together, however, they give the composite part the
Lesson: 4/12
What Is a Matrix?
In a composite, the matrix is the material that binds reinforcing fibers together. Typically the
matrix starts off as a viscous material that hardens to give shape to the composite part and to
protect the fibers from damage. The matrix also transfers the load to the fibers. In essence, the
matrix enhances the support provided by the fibers. Individual filaments, or fiber bundles, provide
little support by themselves. When bound together, however, they give the composite part the
necessary strength and stiffness.
A composite matrix is usually composed of some type of polymer, resin, or plastic. These terms
may be used interchangeably, but there are differences between them. A polymer, shown in Figure
1, describes any group of molecules that are linked to each other in a chain-like structure. Often
polymers occur in groups of chains that are piled together like strands of spaghetti on a plate.
Figure 1. The molecules in a polymer are linked
to each other in a chain-like structure.
A resin is a substance made from synthetic polymers, petrochemicals, or natural plant
secretions. Resins may take the form of viscous liquids or of solid pellets that can be melted and
hardened into rigid parts. In essence, a resin is a polymer that has not been processed into its final
form. Resins are used to make coatings and adhesives. One of the earliest types of resins used
was tree sap, shown in Figure 2.
A plastic is a polymeric material that has been cured into its final form. Thus, a synthetic resin may
be referred to as "plastic" after it has been molded and hardened. However, molded and hardened
resins made from naturally occurring materials are not referred to as plastic, as plastic is made from
synthetic materials only. A synthetic material is artificial and does not occur in nature. For example,
pine sap is a natural material while epoxy is synthetic.
Figure 2. One of the earliest types of resins
used was tree sap.
Lesson: 5/12
Thermoset and Thermoplastic Matrices
The polymers used to form composite matrices come in two types: thermoset and thermoplastic.
A thermoset polymer, shown in Figure 1, cannot be remelted, remolded, or reformed once it has
set, or hardened. This is due to a molecular process called cross-linking that occurs during curing.
Materials that contain cross-linked molecules are highly rigid and thermally stable. Common
thermoset polymers include epoxy, polyester, vinylester, and polyurethane. The advantages of
thermoset polymers include high levels of stability, rigidity, and resistance to chemicals.
In a thermoplastic polymer, like the one in Figure 2, the molecules are not cross-linked, or they are
linked to a weaker degree than in thermosets. The molecules in thermoplastics can be arranged in
either a random or an orderly fashion. Thermoplastic polymers are melted by heating and then
hardened by cooling when taken below their melting temperature. Reshaping or reforming the resin Figure 1. Thermoset polymers contain cross
is done by reheating the polymer. Commonly thermoplastic polymers include nylon,
polypropylene (PP), polyetheretherketone (PEEK), and polyphenylene sulfide (PPS). The main linked molecules.
advantage of thermoplastic polymers is their flexibility.
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Lesson: 5/12
Thermoset and Thermoplastic Matrices
The polymers used to form composite matrices come in two types: thermoset and thermoplastic.
A thermoset polymer, shown in Figure 1, cannot be remelted, remolded, or reformed once it has
set, or hardened. This is due to a molecular process called cross-linking that occurs during curing.
Materials that contain cross-linked molecules are highly rigid and thermally stable. Common
thermoset polymers include epoxy, polyester, vinylester, and polyurethane. The advantages of
thermoset polymers include high levels of stability, rigidity, and resistance to chemicals.
In a thermoplastic polymer, like the one in Figure 2, the molecules are not cross-linked, or they are
linked to a weaker degree than in thermosets. The molecules in thermoplastics can be arranged in
either a random or an orderly fashion. Thermoplastic polymers are melted by heating and then
hardened by cooling when taken below their melting temperature. Reshaping or reforming the resin Figure 1. Thermoset polymers contain cross
is done by reheating the polymer. Commonly thermoplastic polymers include nylon,
polypropylene (PP), polyetheretherketone (PEEK), and polyphenylene sulfide (PPS). The main linked molecules.
advantage of thermoplastic polymers is their flexibility.
Figure 2. Thermoplastic polymers may not be
cross linked.
Lesson: 6/12
What Is a Reinforcement?
The reinforcement is the part of the composite that provides strength, stiffness, and the ability to
carry a load. Reinforcements can be made from whiskers, particles, or fibers. In manufacturing,
fibers are the most commonly used reinforcement. Glass fibers are shown in Figure 1.
A fiber is a hair-like material with a length that is greater than its width or height. Fibers can be
continuous, as in the form of unidirectional and bidirectional fabric, or they can be chopped into
small discontinuous pieces and combined in various formations. The length of the fiber has a
significant impact on the properties of the composite. The longer the fiber, the greater the strength
and flexibility of the composite.
Fibers can be made of carbon, fiberglass, aramid, boron, or other materials such as fabric or
metal. The diameter of a typical fiber ranges from 0.0002 in. (0.0005 cm) to 0.0008 in. (0.0021
cm). The extreme thinness of fibers makes them highly flexible and allows them to be formed into
different shapes. Common types of reinforcements are shown in Figure 2.
Figure 1. In manufacturing, fibers are the most
commonly used reinforcement.
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Lesson: 6/12
What Is a Reinforcement?
The reinforcement is the part of the composite that provides strength, stiffness, and the ability to
carry a load. Reinforcements can be made from whiskers, particles, or fibers. In manufacturing,
fibers are the most commonly used reinforcement. Glass fibers are shown in Figure 1.
A fiber is a hair-like material with a length that is greater than its width or height. Fibers can be
continuous, as in the form of unidirectional and bidirectional fabric, or they can be chopped into
small discontinuous pieces and combined in various formations. The length of the fiber has a
significant impact on the properties of the composite. The longer the fiber, the greater the strength
and flexibility of the composite.
Fibers can be made of carbon, fiberglass, aramid, boron, or other materials such as fabric or
metal. The diameter of a typical fiber ranges from 0.0002 in. (0.0005 cm) to 0.0008 in. (0.0021
cm). The extreme thinness of fibers makes them highly flexible and allows them to be formed into
different shapes. Common types of reinforcements are shown in Figure 2.
Figure 1. In manufacturing, fibers are the most
commonly used reinforcement.
Figure 2. Fibers can be made from materials
such as carbon, fiberglass, and aramid.
Lesson: 7/12
Reinforcement Forms
Composite reinforcements are available in many different forms. Several of these forms are shown
in Figure 1. Reinforcement fibers can be continuous, discontinuous, chopped, or mat. The
differences are as follows:
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U, LLC.the
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fiber covers
entire Reserved.
dimension of a part without a break or interruption.
l Continuous
l Discontinuous fibers are simply fibers that have been cut.
l Chopped fibers are fibers that have been cut into relatively short lengths of 1-3 in. (2.5 to
Lesson: 7/12
Reinforcement Forms
Composite reinforcements are available in many different forms. Several of these forms are shown
in Figure 1. Reinforcement fibers can be continuous, discontinuous, chopped, or mat. The
differences are as follows:
l
l
l
l
Continuous fiber covers the entire dimension of a part without a break or interruption.
Discontinuous fibers are simply fibers that have been cut.
Chopped fibers are fibers that have been cut into relatively short lengths of 1-3 in. (2.5 to
7.6 cm).
A mat is a sheet of material covered with fiber reinforcements, which can be continuous or
discontinuous.
Fibers can also be short or long. A composite may contain only one form of reinforcement, or it
may contain a combination of reinforcement forms. Each form has specific mechanical advantages.
For example, long fibers and continuous fibers are the best choice for structural applications.
The orientation, or direction, of the fibers affects their ability to carry a load. The fibers are
strongest when they are oriented in the same direction as the applied force. For example, if you
had a sheet of composite material with continuous fibers oriented at 0°, the fibers would provide the greatest strength if you applied a pulling force on the left and right sides, as shown in Figure 2.
If you pulled at the material from the top and bottom, however, the load is transfered to the
matrix, which by itself is not as strong as the fibers.
Figure 1. Fibers can be continuous,
discontinuous, chopped, or mat.
Fibers can be oriented in any one direction, or they can be oriented in different directions in
different parts of the composite, or they can be randomly oriented in multiple directions. Different
types of fiber orientation are shown in Figure 3.
Figure 2. Fibers are strongest when they are
oriented in the same direction as the applied
force.
Figure 3. Fibers can be oriented in any one
direction, or in multiple directions.
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direction, or in multiple directions.
Lesson: 8/12
Product Fabrication
Before a composite can be made into a final part or product, it must undergo several processes.
First, the composite is formed, usually through pressure and heat. The matrix and reinforcements
for the composite may be combined before or during the forming process, or they may come in a
pre-combined form.
A prepreg, or pre-impregnated fiber, is a type of ready-made composite. A close-up of a
prepreg is shown in Figure 1. Prepregs use continuous fiber and come in a sheet form that can be
stored until needed. The prepreg is laminated inside the mold, compressed, heated, and cured.
Another type of pre-made composite is molding compound. Molding compounds typically consist
of chopped fiberglass and resin. These are available in sheet form known as sheet molding
compound (SMC), shown in Figure 2, or in a log of bulk material known as bulk molding
compound (BMC), shown in Figure 3.
After the composite has been formed, it typically requires machining. Machining involves drilling,
turning, cutting, or grinding to remove extra material.
Figure 1. Prepregs use continuous fiber and
come in a sheet form that can be stored until
needed.
Joining and assembly occur after machining. During these processes, composites and other
components are joined through adhesive bonding and mechanical fastening. The fourth and
final process is finishing, which includes the application of a coating to the product to protect it
from wear and corrosion.
Figure 2. Sheet molding compound is a type of
pre-made composite.
Figure 3. Bulk molding compound is available in
a putty-like log or in sticky fibers.
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Lesson: 8/12
Product Fabrication
Before a composite can be made into a final part or product, it must undergo several processes.
First, the composite is formed, usually through pressure and heat. The matrix and reinforcements
for the composite may be combined before or during the forming process, or they may come in a
pre-combined form.
A prepreg, or pre-impregnated fiber, is a type of ready-made composite. A close-up of a
prepreg is shown in Figure 1. Prepregs use continuous fiber and come in a sheet form that can be
stored until needed. The prepreg is laminated inside the mold, compressed, heated, and cured.
Another type of pre-made composite is molding compound. Molding compounds typically consist
of chopped fiberglass and resin. These are available in sheet form known as sheet molding
compound (SMC), shown in Figure 2, or in a log of bulk material known as bulk molding
compound (BMC), shown in Figure 3.
After the composite has been formed, it typically requires machining. Machining involves drilling,
turning, cutting, or grinding to remove extra material.
Figure 1. Prepregs use continuous fiber and
come in a sheet form that can be stored until
needed.
Joining and assembly occur after machining. During these processes, composites and other
components are joined through adhesive bonding and mechanical fastening. The fourth and
final process is finishing, which includes the application of a coating to the product to protect it
from wear and corrosion.
Figure 2. Sheet molding compound is a type of
pre-made composite.
Figure 3. Bulk molding compound is available in
a putty-like log or in sticky fibers.
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Lesson: 9/12
Lesson: 9/12
Composite Processing Methods
There are many different ways to process composites. The simplest method is open molding. In
open molding, fibers are put into a single-sided, or "open," mold. Resin is added to the fibers until
they are fully wetted, or saturated. The resin is then cured. The two methods for placing fibers
into the open mold are lay-up molding, shown in Figure 1, and spray-up molding, shown in
Figure 2.
Compression molding, shown in Figure 3, is a closed mold process that uses thermoset resins.
After resin is put into the compression press, the mold closes so that the male half and the
female half squeeze the resin into the contours of the mold. The resin is then simultaneously
pressurized and heated.
Filament winding, shown in Figure 4, is a process in which continuous strands of fiber are fed
from spools into a device that combines them into a band. The band is soaked in resin and passes
through a device that removes excess resin. The band is then wound around a core, or mandrel,
in the desired pattern to form a part.
In pultrusion, fibers are drawn from reels through a resin bath. After the fibers are fully wetted,
they move into a heated die where they are cured. The formed part is then pulled to the final area
of the system for machining and finishing processes.
Other processing methods include injection molding, vacuum bagging, and resin infusion. The
type of method used depends on the type of resin in the matrix (thermoset vs. thermoplastic) and
the length of the fibers in the reinforcement (short vs. continuous).
Figure 1. Lay-up molding is an open mold
method of processing composites.
Figure 2. Spray-up molding is an open mold
method of processing composites.
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method of processing composites.
Figure 3. Compression molding is a closed
mold process.
Figure 4. In filament winding, long fibers are
wound over a mandrel in the desired pattern
to form a part.
Lesson: 10/12
Pros and Cons of Composites
Composites have many advantages. They are lightweight, easily moldable, resistant to fatigue, and
they have a high strength-to-weight ratio. For example, composites can have the strength of
aluminum with only half its weight. In addition, composites are much more resistant to corrosion
and fatigue than metals. The rust shown in Figure 1 is a common cause of corrosion in metal.
Composites also absorb force very well. This gives them natural damping ability during impact,
such as a car crash, as shown in Figure 2. Composites can also be customized to have very specific
properties. Molding allows a high degree of design flexibility in composites. Complex shapes and
detailed contours that would be difficult to form with metals can be easily made with composites. In
addition, molding can reduce the amount of machining required to form the composite into the
desired shape.
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The main disadvantage of composites is cost. Raw material cost for some types of composites is
much higher than for steel or aluminum. In addition, the cost of processing composites can be
Figure 1. Metal is strong but it is vulnerable to
Lesson: 10/12
Pros and Cons of Composites
Composites have many advantages. They are lightweight, easily moldable, resistant to fatigue, and
they have a high strength-to-weight ratio. For example, composites can have the strength of
aluminum with only half its weight. In addition, composites are much more resistant to corrosion
and fatigue than metals. The rust shown in Figure 1 is a common cause of corrosion in metal.
Composites also absorb force very well. This gives them natural damping ability during impact,
such as a car crash, as shown in Figure 2. Composites can also be customized to have very specific
properties. Molding allows a high degree of design flexibility in composites. Complex shapes and
detailed contours that would be difficult to form with metals can be easily made with composites. In
addition, molding can reduce the amount of machining required to form the composite into the
desired shape.
The main disadvantage of composites is cost. Raw material cost for some types of composites is
much higher than for steel or aluminum. In addition, the cost of processing composites can be
higher than for other materials. However, some of this cost can be offset by the advantages that
composites offer.
Figure 1. Metal is strong but it is vulnerable to
corrosion.
Figure 2. The composite materials on this car
were able to absorb the force of the crash.
Lesson: 11/12
Composite Applications
Composites are used in many industries. The greatest demand for composites is in the automotive
industry. Replacing metals with composites makes cars more fuel-efficient because they weigh less.
In addition, the molding capability of composites allows automakers to design cars that are more
aerodynamic.
The aerospace industry makes extensive use of composites. Figure 2 shows a NASA space shuttle
that was made with composites. As with cars, using composites instead of metals in the frame of a
plane makes it more lightweight and fuel efficient. This is especially important in military aircraft
because it allows the planes to take heavier payloads. In addition, the durability of composite
materials makes them well-suited for flight applications. For example, helicopter blades are made of
a fiberglass composite that is extremely resistant to fatigue.
Composites are also widely used in construction and infrastructure applications. Most newly
constructed bridges and roads are made from composite materials. Structures such as electrical
towers, wind turbine blades, and utility light poles are made from composites as well. In addition to
Figure 1. Many car parts are made from
being resistant to corrosion, composite materials are useful in construction and infrastructure
composites.
because of the dwindling supply of natural materials such as trees and metals.
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2011
Tooling U,
LLC. All Rights
Reserved.
The
ability©of
composite
materials
to resist
corrosion makes them extremely useful in the marine
industry. Composites are used to construct boat hulls, masts, tanks, and trailers. The relatively
light weight of composite materials makes them a good choice for marine applications as well.
Lesson: 11/12
Composite Applications
Composites are used in many industries. The greatest demand for composites is in the automotive
industry. Replacing metals with composites makes cars more fuel-efficient because they weigh less.
In addition, the molding capability of composites allows automakers to design cars that are more
aerodynamic.
The aerospace industry makes extensive use of composites. Figure 2 shows a NASA space shuttle
that was made with composites. As with cars, using composites instead of metals in the frame of a
plane makes it more lightweight and fuel efficient. This is especially important in military aircraft
because it allows the planes to take heavier payloads. In addition, the durability of composite
materials makes them well-suited for flight applications. For example, helicopter blades are made of
a fiberglass composite that is extremely resistant to fatigue.
Composites are also widely used in construction and infrastructure applications. Most newly
constructed bridges and roads are made from composite materials. Structures such as electrical
towers, wind turbine blades, and utility light poles are made from composites as well. In addition to
Figure 1. Many car parts are made from
being resistant to corrosion, composite materials are useful in construction and infrastructure
composites.
because of the dwindling supply of natural materials such as trees and metals.
The ability of composite materials to resist corrosion makes them extremely useful in the marine
industry. Composites are used to construct boat hulls, masts, tanks, and trailers. The relatively
light weight of composite materials makes them a good choice for marine applications as well.
Figure 2. The aerospace industry makes
extensive use of composites.
Lesson: 12/12
Summary
A composite is two or more materials that have been combined to create a lightweight material of
superior strength, stiffness, and durability. The reinforcement provides strength, stiffness, and the
ability to carry a load. Fibers are the most commonly used reinforcement in manufacturing. The
matrix is typically some type of polymer, resin, or plastic that binds reinforcing fibers together.
Both thermoset and thermoplastic matrices are used to make composites. A thermoset polymer
cannot be remelted, remolded, or reformed once it has set due to cross-linking that occurs during
curing. In a thermoplastic polymer, the molecules are not cross-linked, or they are linked to a
weaker degree than in thermosets. Thermoplastics can be reshaped or reformed after they have
hardened by reheating the polymer.
Composite reinforcement fibers can be continuous or discontinuous, short or long, chopped or
mat. Fibers can be oriented in any one direction, or they can be oriented in different directions in
different parts of the composite, or they can be randomly oriented in multiple directions.
Before a composite can be made into a final part or product, it must undergo several processes. In
the first step, the composite is formed. The second step is machining, while the third is joining and
Copyright ©The
2011
Tooling
U, final
LLC. step
All Rights
Reserved.
assembly.
fourth
and
is finishing.
There are many different ways to process composites, including lay-up molding, spray-up molding,
Figure 1. Fibers are the most commonly used
reinforcement in manufacturing.
Lesson: 12/12
Summary
A composite is two or more materials that have been combined to create a lightweight material of
superior strength, stiffness, and durability. The reinforcement provides strength, stiffness, and the
ability to carry a load. Fibers are the most commonly used reinforcement in manufacturing. The
matrix is typically some type of polymer, resin, or plastic that binds reinforcing fibers together.
Both thermoset and thermoplastic matrices are used to make composites. A thermoset polymer
cannot be remelted, remolded, or reformed once it has set due to cross-linking that occurs during
curing. In a thermoplastic polymer, the molecules are not cross-linked, or they are linked to a
weaker degree than in thermosets. Thermoplastics can be reshaped or reformed after they have
hardened by reheating the polymer.
Composite reinforcement fibers can be continuous or discontinuous, short or long, chopped or
mat. Fibers can be oriented in any one direction, or they can be oriented in different directions in
different parts of the composite, or they can be randomly oriented in multiple directions.
Figure 1. Fibers are the most commonly used
reinforcement in manufacturing.
Before a composite can be made into a final part or product, it must undergo several processes. In
the first step, the composite is formed. The second step is machining, while the third is joining and
assembly. The fourth and final step is finishing.
There are many different ways to process composites, including lay-up molding, spray-up molding,
compression molding, filament winding, pultrusion, injection molding, vacuum bagging, and resin
infusion. The type of method used depends on the type of resin in the matrix and the length of the
fibers in the reinforcement.
Composites are lightweight, easily moldable, resistant to fatigue, and have a high strength-toweight ratio. They also absorb force very well and can be customized to have very specific
properties. The main disadvantage of composites is cost. However, some of this cost can be offset by the advantages that composites offer. Composites are used in the automotive industry,
aerospace industry, construction and infrastructure applications, and the marine industry, among
others.
Figure 2. Composite reinforcements come in
many different forms.
Figure 3. Composite parts absorb force very
well.
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Class Vocabulary
Term
Definition
Class Vocabulary
Term
Definition
Adhesive Bonding
Aerodynamic
Alloy
Applied Force
Aramid
Boron
Bulk Molding Compound
Carbon
Ceramic
Chopped
Composite
Compression Molding
Compression Press
Continuous
Cross-Linking
Cured
Cutting
Damping Ability
Discontinuous
The joining of two or more materials with a nonmetallic substance such as liquids, drops, or gels.
Having a design that reduces friction and resistance.
A metal consisting of a mix of two or more elements, one of which must be a metal.
The energy or effort provided to a machine to perform work.
A type of fiber with strong heat resistance that is used primarily in aerospace and military applications.
A metallic element having a marked effect on hardenability even in minute quantities.
BMC. A molding compound that combines a resin, initiator, filler, and reinforcement into a block of sticky
dough-like material.
A non-metallic chemical element used in composite reinforcements.
A hard, brittle material that can withstand high temperatures and resist corrosion.
Discontinuous pieces of fiber that have been cut into lengths of 1-3 in. (2.5 to 7.6 cm).
A material that is made by combining a binding resin with small filaments of solid material. Composites have
the strength of metal, the light weight of plastic, and the rigidity of ceramics.
A molding process in which reinforcement is saturated with resin and subjected to pressure and heat to create
a finished part.
The machine in which compression molding takes place.
Covering the entire dimension of a part without a break or interruption. Continuous fibers are used in mat and
cloth reinforcements.
The development of primary bonds that form between polymer molecules. Thermosets are heavily crosslinked, while thermoplastics are not cross-linked, or they are cross-linked to a weaker degree.
Having permanently cross-linked molecules. Curing occurs in thermosets when they are heated to mold.
A machining process that uses a tool to create chips and remove metal from a workpiece.
The ability to dissipate energy. Damping is usually used to absorb shock and reduce vibration.
Chopped or cut. Discontinuous fibers can be applied to a mat or sprayed on to a surface with a special gun.
Drilling
The process of using a multi-point tool to penetrate the surface of a workpiece and make a round hole.
Ductile
Able to be drawn, stretched, or formed without breaking.
Epoxy
A high-strength adhesive, often made of two different materials that must be mixed together just prior to
use.
Fiber
Fiberglass
Filament
A reinforcing material whose length is greater than its height or width. Fibers are larger than whiskers or
particles.
Reinforcement material made from extremely fine strands of glass. Fiberglass is the most commonly used
composite reinforcement.
An extremely thin strand of material. Filaments can be combined into a larger strand called a fiber.
Filament Winding
A process in which strands of fiber are soaked in resin and wound around a core in the desired pattern to
create a part.
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Finishing
The treatment of a surface to remove roughness and irregularities and improve its appearance.
Filament Winding
A process in which strands of fiber are soaked in resin and wound around a core in the desired pattern to
create a part.
Finishing
The treatment of a surface to remove roughness and irregularities and improve its appearance.
Grinding
The use of an abrasive to remove minor imperfections and bring a part to its final finish tolerance.
Injection Molding
A molding process in which resin is heated in a barrel and then injected into a mold by a reciprocating screw.
The resin then cools in the mold and is ejected as a solid part.
Lay-Up Molding
A manual molding process in which reinforcement in the form of a fabric or a mat is positioned into the mold
and saturated with a resin.
Load
Mandrel
Mat
Matrix
Mechanical Fastening
Metal
Molding Compound
Molecule
Nylon
Open Molding
Orientation
Particle
Petrochemical
Plastic
Polyester
Polyetheretherketone
Polymer
Polyphenylene Sulfide
Polypropylene
Polyurethane
Pre-Impregnated Fiber
Prepreg
Pultrusion
The overall force applied to a material or structure. In a composite, the matrix transfers the load to the
reinforcement fibers.
The core around which resin-impregnated fiber is wound.
A sheet of material covered with fiber reinforcements. Reinforcements can be discontinuous (chopped) or
continuous.
The material that binds together the reinforcing fibers of a composite. The matrix is usually a viscous material
that hardens to give shape to the composite part and to protect the fibers from damage.
A process that joins two materials through the use of screws, bolts, and nails.
A naturally occurring material with high electric and thermal conductivity, luster, density, and strength.
Examples of metal include copper, iron, nickel, and lead.
A type of ready-made composite in which the matrix and reinforcement have already been combined. Molding
compound is available in bulk form and in sheet form.
Two or more atoms joined together by chemical bonds. A molecule is the smallest amount of a specific
chemical substance that can exist alone.
An artificial material made from polymers. Nylon is extremely strong and resilient.
A molding process in which fibers are put into a single-sided or open mold. Resin is added to the fibers and
the part is cured at room temperature or with heat.
The direction or lay of a reinforcement fiber.
An extremely small piece or part. Particles are smaller than whiskers or fibers.
A compound made from petroleum or natural gas. Petrochemicals can be used to make matrix resins.
A synthetic polymer that can be molded and hardened into a variety of shapes.
A type of thermoset that is commonly combined with other polymers for numerous commercial uses. Polyester
is light, strong, and resistant to weather and corrosion.
PEEK. An organic thermoplastic polymer used to fabricate items for high-performance applications. PEEK is
extensively used in the aerospace, automotive, teletronic, and chemical process industries.
A group of molecules that are linked to each other in a chain-like structure. Polymers are used to create
composite matrices.
PPS. A thermoplastic resin used primarily in compression and injection molding. PPS is extremely resistant to
corrorsion.
A type of thermoplastic known for being very lightweight.
A type of plastic that is often chemically complex. Polyurethane is used for padding and insulation in furniture,
clothing, and packaging, and in the manufacture of resins for adhesives, elastomers, and fillers.
Prepreg. Reinforcement material that has already been saturated with resin.
Pre-impregnated fiber. Reinforcement material that has already been saturated with resin.
A molding process in which heated resin cures as it is pulled through a die. Pultrusion is a variation of the
extrusion process, during which resin is pushed through a die.
Reinforcement
partReserved.
of the composite that provides strength, stiffness, and the ability to carry a load. In manufacturing,
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Rights
fibers are the most commonly used reinforcement.
Resin
A substance made from either synthetic or natural polymers and used for composite matrices. In essence, a
extrusion process, during which resin is pushed through a die.
Reinforcement
Resin
Resin Infusion
Rigid
Sheet Molding Compound
Spray-Up Molding
Synthetic
Thermoplastic
Thermoset
Turning
Vacuum Bagging
Vinylester
The part of the composite that provides strength, stiffness, and the ability to carry a load. In manufacturing,
fibers are the most commonly used reinforcement.
A substance made from either synthetic or natural polymers and used for composite matrices. In essence, a
resin is a polymer that has not been processed into its final form.
A type of molding in which a dry fiber preform is placed into a mold. Resin is injected into the mold until it
saturates the preform and the part is cured.
Unable to bend or resistant to bending.
SMC. A rolled-up sheet in which the ingredients are not mixed together all at once. Instead, a pre-mixed, preinitiated paste of resin and filler is applied to a moving sheet of film onto which strands of fiberglass are
applied.
A manual molding process in which an operator uses a spray machine to simultaneously apply resin and
chopped fiberglass strands to an open mold.
Not of natural origin. Artificial or human-made. Nylon is a synthetic material while cotton is a natural material.
A polymer in which the molecules are not cross-linked, or they are cross-linked to a weaker degree. A
thermoplastic polymer can be reshaped or reformed by reheating the polymer.
A polymer that cannot be remelted or reformed once it has cured, due to a molecular process called crosslinking that occurs during curing.
An operation performed on a lathe that feeds a cutting tool along the length of a cylindrical part to reduce its
diameter.
A type of compression molding in which a bag is placed over the mold and the vacuum compresses the bag
and squeezes out any air or excess resin.
A synthetic resin that forms a chain of molecules around a fiber.
Viscous
Having a high resistance to flow. Viscous fluids tend to be sticky or syrupy.
Wetted
Having full contact between a fluid and a surface. Fiber reinforcement must be saturated with matrix resin in
order to be fully wetted.
Whisker
A short, thin filament used for composite reinforcements. Whiskers are smaller than fibers.
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