**1. Introduction**

Composites exist in nature. A piece of wood is a composite, with long cellulose fibres held together by a substance called lignin. Composite materials are formed by combining two or more materials that have quite different properties, and they do not dissolve or blend into each other. The different materials in the composite work together to give the composite unique properties. Humans have been using composite materials for thousands of years in different areas. The first uses of composites date back to the 1500 BC, when early Egyptians and Mesopotamian settlers used a mixture of mud and straw to create strong and durable buildings. The combination of mud and straw in a block of brick provides it a strong property against both squeezing and tearing or bending. The straw continued to provide reinforcement to ancient composite products, including pottery and boats [1]. In 1200 AD, the Mongols invented the first composite bow using a combination of "animal glue", bone, and wood. The bows were pressed and wrapped with birch bark. These bows were powerful and accurate. Composite Mongolian bows helped to ensure Genghis Khan's military dominance. Due to their advantages such as being light weight and strong, many of the greatest advancements in composites were the result of wartime needs. During World War II, many composite materials were developed and moved from the laboratory into actual production [1, 2].

The development and need for composite materials also result in the fibrereinforced polymers (FRP) industry. By 1945, more than 7 million pounds of glass

Any material can serve as a matrix material for composite. However, matrix materials are generally ceramics, metals, and polymers. In reality, the majority of matrix materials that exist on the composites market are polymer. There are several different polymer matrices which can be utilised in composite materials. Among the polymer matrix composites, thermoset matrix composites are more predominant than thermoplastic composites. Though thermoset and thermoplastics sound similar, they have very different properties and applications. Understanding the performance differences can help to make better sourcing decisions and the product

Thermosets are materials that undergo a chemical reaction or curing and normally transform from a liquid to a solid. In its uncured form, the material has small, unlinked molecules known as monomers. The addition of a second material as a cross-linker, curing agent, catalyst, and/or the presence of heat or some other activating influences will initiate the chemical reaction or curing reaction. During this reaction, the molecules cross-link and form significantly longer molecular chains and cross-link network, causing the material to solidify. The change of the thermoset state is permanent and irreversible. Subsequently, exposure to high heat after solidifying will cause the material to degrade, not melt. This is because these materials typically degrade at a temperature below where it would be able

Thermoplastics are melt-process able plastics. The thermoplastic materials are processed with heat. When enough heat is added to bring the temperature of the plastic above its melting point, the plastic melts, liquefies, or softens enough to be processed. When the heat source is removed and the temperature of the plastic drops below its melting point, the plastic solidifies back into a glasslike solid. This process can be repeated, with the plastic melting and solidifying as the temperature climbs above and drops below the melting temperature, respectively. However, the material can be increasingly subject to deterioration in its molten state, so there is a practical limit to the number of times that this reprocessing can take place before the material properties begin to suffer. Many thermoplastic polymers are additiontype, capable of yielding very long molecular chain lengths or very high molecular

Both thermoset and thermoplastic materials have its place in the market. In broad generalities, thermosets tend to have been around for a long time and have a well-established place in the market, frequently have lower raw material costs, and often provide easy wetting of reinforcing fibre and easy forming to final part geometries. In other words, thermosets are often easier to process than thermoplastic. Thermoplastics tend to be tougher or less brittle than thermoset. They can have better chemical resistance, do not need refrigeration as uncured thermosets (prepreg materials) frequently do, and can be more easily recycled and repaired. **Table 1** presents a comparison between thermoset and thermoplastic. This table is not providing all but rather some information for the researchers and manufac-

Thermosets are classified into polyester resins, epoxy resins, vinyl ester resins, phenolic, polyurethane, and other high-temperature resins such as cyanate esters, etc. The rapid industrialisation in developing economies the world over is one of the major boosting factors for the thermoset market. The demand for highperformance and lightweight materials from various end-use industries such as automotive, chemical tanks, and water tanks is expected to expand the global market for thermosets over the next 6 years. The growing demand for thermosets from emerging economies like Brazil, Russia, India, and China (BRIC) is expected to drive the market. BRIC nations are the four fastest-growing economies in the world with their GDP growth rates higher than the global GDP growth rate.

turers when considering the utilisation of these materials.

designs as composites [11].

*Introduction to Composite Materials*

*DOI: http://dx.doi.org/10.5772/intechopen.91285*

to melt.

weights [12].

**5**

fibres were used for various products, primarily for military applications. Composite materials continued to take off after the war and grew rapidly through the 1950s. The composite innovators were ambitiously trying to introduce composites into other markets such as aerospace, construction, and transportation. Soon the benefits of FRP composites, especially its corrosion resistance, became known to the public sector. Boats were one obvious product that benefited. The first composite commercial boat hull was introduced in 1946. A full automobile body was made from composite and tested in 1947 [1, 2]. This led to the development of the 1953 Chevrolet Corvette. The advent of the automobile age gave rise to several new methods for moulding such as compression moulding of bulk moulding compound (BMC) and sheet moulding compound (SMC). The two techniques emerged as the dominant method of moulding for the automotive industry and other industries. In the early 1950s, manufacturing methods such as large-scale filament winding, pultrusion, and vacuum bag moulding were developed. In the 1960s, the marine market became the largest consumer of composite materials [1, 2]. In 1961, the first carbon fibre was patented and several years later became commercially available. In the 1970s the composites industry began to mature. Many better resins and improved reinforcing fibres were developed during this period for composite applications. In the 1970s, the automotive market surpassed marine as the number one market—a position it retains today. During the late 1970s and early 1980s, composites were first used in infrastructure applications in Asia and Europe. The first all-composites pedestrian bridge was installed in Aberfeldy, Scotland, in the 1990s. In this period, the first FRP-reinforced concrete bridge deck was built in McKinleyville, West Virginia, and the first all-composites vehicular bridge deck was built in Russell, Kansas. Composites continue to find applications today [1–3]. Nanomaterials are incorporated into improved fibres and resins used in new composites. Nanotechnology began to be used in commercial products in the early 2000s. Bulk carbon nanotubes can be used as composite reinforcement in polymers to improve the mechanical, thermal, and electrical properties of the bulk product [3].

Nowadays, the composite industry is still evolving, with much of the growth now focused around renewable energy. Wind turbine blades, especially, are constantly pushing the limits on size and require advanced composite materials, for example, the engineers can design to tailor the composite based on the performant requirements, making the composite sheet very strong in one direction by aligning the fibres that way, but weaker in another direction where strength is not so important. The engineers can also select properties such as resistance to heat, chemicals, and weathering by choosing an appropriate matrix material. In recent years, an increasing environmental consciousness and awareness of the need for sustainable development have raised interest in using natural fibres as reinforcements in composites to replace synthetic fibres [4–7]. This chapter seeks to provide an overview of the science and technology in relation to the composite material, manufacturing process, and utilisation.

### **2. Polymer matrix**

In general, a composite consists of three components: (i) the matrix as the continuous phase; (ii) the reinforcements as the discontinuous or dispersed phase, including fibre and particles; and (iii) the fine interphase region, also known as the interface [8, 9]. By carefully choosing the matrix, the reinforcement, and the manufacturing process that brings them together, the engineers can tailor the properties to meet specific requirements [10]. Over the recent decades, many new composites have been developed, some with very valuable properties.

#### *Introduction to Composite Materials DOI: http://dx.doi.org/10.5772/intechopen.91285*

fibres were used for various products, primarily for military applications. Composite materials continued to take off after the war and grew rapidly through the 1950s. The composite innovators were ambitiously trying to introduce composites into other markets such as aerospace, construction, and transportation. Soon the benefits of FRP composites, especially its corrosion resistance, became known to the public sector. Boats were one obvious product that benefited. The first composite commercial boat hull was introduced in 1946. A full automobile body was made from composite and tested in 1947 [1, 2]. This led to the development of the 1953 Chevrolet Corvette. The advent of the automobile age gave rise to several new methods for moulding such as compression moulding of bulk moulding compound (BMC) and sheet moulding compound (SMC). The two techniques emerged as the dominant method of moulding for the automotive industry and other industries. In the early 1950s, manufacturing methods such as large-scale filament winding, pultrusion, and vacuum bag moulding were developed. In the 1960s, the marine market became the largest consumer of composite materials [1, 2]. In 1961, the first carbon fibre was patented and several years later became commercially available. In the 1970s the composites industry began to mature. Many better resins and improved reinforcing fibres were developed during this period for composite applications. In the 1970s, the automotive market surpassed marine as the number one market—a position it retains today. During the late 1970s and early 1980s, composites were first used in infrastructure applications in Asia and Europe. The first all-composites pedestrian bridge was installed in Aberfeldy, Scotland, in the 1990s. In this period, the first FRP-reinforced concrete bridge deck was built in McKinleyville, West Virginia, and the first all-composites vehicular bridge deck was built in Russell, Kansas. Composites continue to find applications today [1–3]. Nanomaterials are incorporated into improved fibres and resins used in new composites. Nanotechnology began to be used in commercial products in the early 2000s. Bulk carbon nanotubes can be used as composite reinforcement in polymers to improve the mechanical, thermal, and elec-

*Composite and Nanocomposite Materials - From Knowledge to Industrial Applications*

Nowadays, the composite industry is still evolving, with much of the growth now focused around renewable energy. Wind turbine blades, especially, are constantly pushing the limits on size and require advanced composite materials, for example, the engineers can design to tailor the composite based on the performant requirements, making the composite sheet very strong in one direction by aligning the fibres that way, but weaker in another direction where strength is not so important. The engineers can also select properties such as resistance to heat, chemicals, and weathering by choosing an appropriate matrix material. In recent years, an increasing environmental consciousness and awareness of the need for sustainable development have raised interest in using natural fibres as reinforcements in composites to replace synthetic fibres [4–7]. This chapter seeks to provide an overview of the science and technology in relation to the composite material,

In general, a composite consists of three components: (i) the matrix as the continuous phase; (ii) the reinforcements as the discontinuous or dispersed phase, including fibre and particles; and (iii) the fine interphase region, also known as the interface [8, 9]. By carefully choosing the matrix, the reinforcement, and the manufacturing process that brings them together, the engineers can tailor the properties to meet specific requirements [10]. Over the recent decades, many new

composites have been developed, some with very valuable properties.

trical properties of the bulk product [3].

manufacturing process, and utilisation.

**2. Polymer matrix**

**4**

Any material can serve as a matrix material for composite. However, matrix materials are generally ceramics, metals, and polymers. In reality, the majority of matrix materials that exist on the composites market are polymer. There are several different polymer matrices which can be utilised in composite materials. Among the polymer matrix composites, thermoset matrix composites are more predominant than thermoplastic composites. Though thermoset and thermoplastics sound similar, they have very different properties and applications. Understanding the performance differences can help to make better sourcing decisions and the product designs as composites [11].

Thermosets are materials that undergo a chemical reaction or curing and normally transform from a liquid to a solid. In its uncured form, the material has small, unlinked molecules known as monomers. The addition of a second material as a cross-linker, curing agent, catalyst, and/or the presence of heat or some other activating influences will initiate the chemical reaction or curing reaction. During this reaction, the molecules cross-link and form significantly longer molecular chains and cross-link network, causing the material to solidify. The change of the thermoset state is permanent and irreversible. Subsequently, exposure to high heat after solidifying will cause the material to degrade, not melt. This is because these materials typically degrade at a temperature below where it would be able to melt.

Thermoplastics are melt-process able plastics. The thermoplastic materials are processed with heat. When enough heat is added to bring the temperature of the plastic above its melting point, the plastic melts, liquefies, or softens enough to be processed. When the heat source is removed and the temperature of the plastic drops below its melting point, the plastic solidifies back into a glasslike solid. This process can be repeated, with the plastic melting and solidifying as the temperature climbs above and drops below the melting temperature, respectively. However, the material can be increasingly subject to deterioration in its molten state, so there is a practical limit to the number of times that this reprocessing can take place before the material properties begin to suffer. Many thermoplastic polymers are additiontype, capable of yielding very long molecular chain lengths or very high molecular weights [12].

Both thermoset and thermoplastic materials have its place in the market. In broad generalities, thermosets tend to have been around for a long time and have a well-established place in the market, frequently have lower raw material costs, and often provide easy wetting of reinforcing fibre and easy forming to final part geometries. In other words, thermosets are often easier to process than thermoplastic. Thermoplastics tend to be tougher or less brittle than thermoset. They can have better chemical resistance, do not need refrigeration as uncured thermosets (prepreg materials) frequently do, and can be more easily recycled and repaired. **Table 1** presents a comparison between thermoset and thermoplastic. This table is not providing all but rather some information for the researchers and manufacturers when considering the utilisation of these materials.

Thermosets are classified into polyester resins, epoxy resins, vinyl ester resins, phenolic, polyurethane, and other high-temperature resins such as cyanate esters, etc. The rapid industrialisation in developing economies the world over is one of the major boosting factors for the thermoset market. The demand for highperformance and lightweight materials from various end-use industries such as automotive, chemical tanks, and water tanks is expected to expand the global market for thermosets over the next 6 years. The growing demand for thermosets from emerging economies like Brazil, Russia, India, and China (BRIC) is expected to drive the market. BRIC nations are the four fastest-growing economies in the world with their GDP growth rates higher than the global GDP growth rate.

composite material relative to thermoset polymers, is a growing material trend in the fibre-reinforced polymer (FRP) industry. According to the American Composites Manufacturers Association (ACMA), the thermoplastic industry is expected to grow 4.9% over the next years and reach an estimated \$8.2 billion by 2017, with even larger opportunities in emerging economies. Thermoplastic polymers also offer an easy solution to recycling composite components, a concern when it comes to adopting composite materials. Thermoplastic composites can repeat the heating and cooling cycle many times, thus giving the product an almost indefinite shelf life and adding more value for industries concerned with composite recyclability. This is especially the case for the growth of natural fibre thermoplastics in the USA and Western Europe. For example, wood-plastic composites, used for decking material and other wood substitutions, have grown by 35–40% in the past 5 years. According to Lucintel (the premier global management consulting and market research firm), countries in Asia and Eastern Europe will lead the growth for thermoplastic adoption because automotive production and thermoplastic automotive component production are quickly growing in those regions. However, the automotive sectors in the USA and Western Europe may not experience the same high rate of growth but are expected to develop steadily in the next 5 years, mainly due to the acceptance of new composite application. The study indicates that although gains will be limited by rising energy costs and competition from lower cost materials, there is significant opportunity in emerging economies such as China, Russia, Brazil, and India [15]. Recently, a major trend in the aerospace industry is a move toward greater use of thermoplastics vs. "traditional" thermoset epoxies. This also opens an opportu-

Thermoplastic are the dominant plastic materials overall, especially in nonreinforced applications. Thermosets are used in non-reinforced applications for a specific purpose where they have an advantage because of some unique property. However, within the reinforced or composites marketplace, thermoset dominant and thermoplastic are used only in applications where their unique advantages are important. Within the composite market, thermoset represents about 80% of the total material used [16]. The global composite resin market size by end-use applications, in terms of value, was USD 9317.4 Million in 2014 and is projected to grow

As mentioned above, thermoplastics are capable of being repeatedly softened by the application of heat and hardened by cooling and have the potential to be the most easily recycled, which has seen them most favoured in recent commercial uptake, whereas better realisation of the fibre properties is generally achieved using thermosets. There are several types of polymers in the market. The most common

Composite reinforcements can be in various forms such as fibres, flakes, or particles. Each of these has its own properties which can be contributed to the composites, and therefore, each has its own area of applications. Among the forms, fibres are the most commonly used in composite applications, and they have the most influence on the properties of the composite materials. These reasons are that the fibres have the high aspect ratio between length and diameter, which can provide effective shear stress transfer between the matrix and the fibres, and the ability to process and manufacture the composites part in various shapes using

nity for thermoplastics.

*Introduction to Composite Materials*

*DOI: http://dx.doi.org/10.5772/intechopen.91285*

**3. Reinforcements**

different techniques.

**7**

at a CAGR of 5.6% between 2015 and 2020 [17].

polymers are summarized in **Table 2** [18–23].


#### **Table 1.**

*Thermoset vs. thermoplastic.*

However, frequent fluctuation in raw material prices acts as one of the major factors inhibiting the market growth. Asia-Pacific accounts for the biggest market for thermosets owing to the growth of the automobile market, primarily in China and India. Japan is a mature market and is expected to remain stagnant over the next years. China is the biggest automobile market in the world, and India also lists itself in the top five automobile markets in the world. Asia, along with being the largest market, is also the fastest-growing market for thermosets. The North American market for thermosets is primarily driven by the regulatory initiative to reduce automobile weight by 50% by 2020 in the USA in order to cut fuel consumption. Polyester resins and polyurethane account for the two most popular types of thermosets in the global market. The global market for thermosets is dominated by big multinational corporations which are present across the value chain. Some of the major companies operating in the thermosets market include Arkema, BASF, Asahi Kasei Chemical Corp, Bayer AG, Chevron Phillips Chemical Company LLC, Sinopec, Dow Chemical Company, Eastman Chemical Company, and Lyondell Basell Industries, among others [13]. To date, thermosets have been used predominantly in the industry. Thermosets are generally favoured for a variety of reasons, especially on commercial aircraft. Thermoset composites have been used for 30–40 years in aerospace. For example, the fuselage of the Boeing 787 is an epoxy-based polymer [14].

On the other hand, the use of thermoplastic polymers (acrylic, polyolefin, acrylonitrile butadiene styrene (ABS), etc.), the more easily moldable and resettable

#### *Introduction to Composite Materials DOI: http://dx.doi.org/10.5772/intechopen.91285*

composite material relative to thermoset polymers, is a growing material trend in the fibre-reinforced polymer (FRP) industry. According to the American Composites Manufacturers Association (ACMA), the thermoplastic industry is expected to grow 4.9% over the next years and reach an estimated \$8.2 billion by 2017, with even larger opportunities in emerging economies. Thermoplastic polymers also offer an easy solution to recycling composite components, a concern when it comes to adopting composite materials. Thermoplastic composites can repeat the heating and cooling cycle many times, thus giving the product an almost indefinite shelf life and adding more value for industries concerned with composite recyclability. This is especially the case for the growth of natural fibre thermoplastics in the USA and Western Europe. For example, wood-plastic composites, used for decking material and other wood substitutions, have grown by 35–40% in the past 5 years. According to Lucintel (the premier global management consulting and market research firm), countries in Asia and Eastern Europe will lead the growth for thermoplastic adoption because automotive production and thermoplastic automotive component production are quickly growing in those regions. However, the automotive sectors in the USA and Western Europe may not experience the same high rate of growth but are expected to develop steadily in the next 5 years, mainly due to the acceptance of new composite application. The study indicates that although gains will be limited by rising energy costs and competition from lower cost materials, there is significant opportunity in emerging economies such as China, Russia, Brazil, and India [15]. Recently, a major trend in the aerospace industry is a move toward greater use of thermoplastics vs. "traditional" thermoset epoxies. This also opens an opportunity for thermoplastics.

Thermoplastic are the dominant plastic materials overall, especially in nonreinforced applications. Thermosets are used in non-reinforced applications for a specific purpose where they have an advantage because of some unique property. However, within the reinforced or composites marketplace, thermoset dominant and thermoplastic are used only in applications where their unique advantages are important. Within the composite market, thermoset represents about 80% of the total material used [16]. The global composite resin market size by end-use applications, in terms of value, was USD 9317.4 Million in 2014 and is projected to grow at a CAGR of 5.6% between 2015 and 2020 [17].

As mentioned above, thermoplastics are capable of being repeatedly softened by the application of heat and hardened by cooling and have the potential to be the most easily recycled, which has seen them most favoured in recent commercial uptake, whereas better realisation of the fibre properties is generally achieved using thermosets. There are several types of polymers in the market. The most common polymers are summarized in **Table 2** [18–23].
