An Introduction to Composite Materials
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What is a Composite Material?
Composite materials are the combination of two or more materials that have their unique properties. Different types of composite materials are in use today, meeting the challenges and requirements of a technologically advanced world. For example applications of composite materials can be found ranging from space shuttles to huge construction sites.
Another reason for the increase in the uses of composite materials, apart from the combined characteristics of materials are properties, such as being less expensive, light in weight, and stronger when compared to common materials. Therefore, the applications of composite materials are found in diverse fields falling under the material application definition i.e. requiring materials to achieve the making of an object with specified properties.
Definition of Composite Materials
The composite material definition can be simply made from the introduction of composite materials. Thus, composite materials are the materials that are produced from the combination of two or more constituent materials. Although the constituent materials might have different and unique properties, they are merged together to form material unlike the individual materials and having the beneficial properties of all the constituents.
The difference between composite materials and mixtures and solid solutions is that within the end product the individual components remain separate and distinct. Thus, composite materials meaning includes in the characteristics of composite materials, the unique properties of a material without actually fusing them into one another.
Some of the typical examples of composite materials include:
Reinforced concrete,
Wooden composite materials
Ceramic material composites
Metal composite matrix
Reinforced plastics, etc.
Other uses of composite materials based on the characteristics of composite material include in construction of buildings and bridges, making of the space shuttles, boats, bathtubs, storage tanks, racing cars, aircraft, etc. With the introduction of sensing, actuation, computation, and higher-order communication in between the materials, it is used in creating components of robots and satellites as well. These are specialized applications of composite materials. With the development of material sciences, they are also used in the manufacturing of daily use gadgets such as mobile phones, drones, laptops, etc.
Let’s Take Another Example:
For instance, if you are preparing concrete for commercial purposes, you need to mix it in quite a small quantity. Before it gets ready for pouring, each concrete must go through the common mixing procedure. It is up to the user whether he wants to buy a bag of cement or it will be an equal blend of gravel, sand, or cement. In case the user purchases the wet concrete, it will be sent to him mixed with water in the form of a semi-liquid mixture. It will reach you in big trucks that are equipped with rotational cylindrical beds for keeping the mixture safe from hardening.
History of Composite Materials
Since time immemorial, applications of composite materials have been numerous. One of the earliest composite materials was the bricks made from straw and mud for building construction. Also, one of the most widely used composite materials, concrete, has been in use since ancient times around 25 BCE. Woody composite materials made up of wood from true trees and plants such as palms and bamboo have been used since ancient times for making up scaffolding structures. Another such example is the use of plywood which has been in use since the ancient Mesopotamian civilization. All these examples of applications of composite materials provide a long connection with the needs of mankind of composite materials.
The technology of composite materials saw new transformations like the invention of fibreglass. It is made up of glass fibres and polymeric materials, such as epoxy or polyester, providing stiffness, strength, flexibility, and durability to the finished product - a combination of both constituent materials. In 1935, the first artificial reinforced plastic composite was produced using fibreglass and bakelite. Glass and plastic film over the thin electrical conductors made up of indium tin oxide make up the touch screens of the very commonly used smartphones and tablets. All this demonstrates a long and continuing journey of the use of different types of composites by mankind.
Making up and Classification of Composite Materials
As understood from the composite material definition, a composite material is made up of two or more constituent materials. The classification of composite materials depends upon the two types of categories of constituent materials, which are the matrix and the reinforcement. An optimal combination of a variety of matrix and reinforcement materials is used to make composite materials that impart the required characteristics of composite materials. The matrix provides support to the reinforcement and the reinforcement, in turn, imparts its own physical and mechanical properties to the matrix. Thus, both the matrix and the reinforcement provide durability, sustainability, and utility to the composite material meaning. The classification of composite materials based on their matrix and reinforcement type is given below:
For making the composite material, the reinforcement is placed on a mould surface or cavity. Depending on the matrix material, it is introduced to the reinforcement after or before being placed in the mould. Following this, the matrix undergoes a melding event setting up the required shape of the composite material. This melding can happen in several ways, such as solidification in the case of melting thermoplastic polymer matrix and chemical polymerization in the case of the thermoset polymer matrix. This process is the formation step of engineered composite materials. The moulding methods used depend on the requirements of the end-product. The nature of matrix and reinforcement materials influence this step which later defines the characteristics of composite materials.
Apart from the nature of the chosen material for the matrix and reinforcement, another factor that influences the moulding process is the gross quantities of material. For example, rapid and automated manufacturing technologies involving high investments, require large quantities of gross materials whereas for producing small quantities involving low investments and high labour the gross quantities required are less. Examples of a commercially used matrix material are resin which is a polymer matrix material that can be used for different moulding methodologies depending on the amount of monetary investment. The moulding processes are also influenced in small amounts by the types of composite materials that are needed to be produced.
Conclusion
A brief understanding of the composite material and different types of composite materials which are classified based on unique properties and characteristics of composite materials required in the end-use is gained in this article. Also, the making of the composite material explains the nature of the composite material that is obtained from the constituent materials. The importance of the composite material and its utilization since ancient times underlines the importance of the composite materials as well.
FAQs on Composite Materials
1. What is a composite material in basic terms?
A composite material is a structural material formed by combining two or more different materials with distinct physical or chemical properties. The individual components remain separate and distinct within the final structure. The goal is to create a new material with enhanced properties, such as being stronger, lighter, or more durable than the original components alone. A composite typically consists of a reinforcement (like fibres or particles) and a matrix (the binder that holds it all together).
2. How are composite materials classified based on their matrix?
Composite materials are primarily classified based on the type of matrix material used. The main categories are:
- Polymer Matrix Composites (PMCs): These use a polymer resin as the matrix. They are the most common type, known for being lightweight and corrosion-resistant. Examples include fibreglass and carbon fibre composites.
- Metal Matrix Composites (MMCs): These use a metal, such as aluminium or titanium, as the matrix. They offer high strength and resistance to high temperatures.
- Ceramic Matrix Composites (CMCs): These use a ceramic as the matrix. They are exceptionally resistant to heat and wear, making them suitable for high-temperature applications like jet engine components.
3. What are some examples of composite materials used in everyday life?
Many common materials are composites. Some key examples include:
- Reinforced Concrete: Steel bars (reinforcement) are embedded in concrete (matrix) to provide tensile strength.
- Fibreglass: Glass fibres are embedded in a polymer matrix, used in boats, car bodies, and surfboards.
- Carbon Fibre Reinforced Polymer (CFRP): Extremely strong and lightweight, used in high-performance sports equipment, racing cars, and aircraft.
- Plywood: Sheets of wood veneer are glued together with their grains at right angles, creating a strong and stable panel.
4. What are the key properties and advantages of using composite materials?
The primary advantage of composite materials is their superior strength-to-weight ratio. They can be as strong as steel but significantly lighter. Other important properties include:
- High Durability: They are resistant to damage, rust, and corrosion.
- Design Flexibility: Composites can be moulded into complex shapes, which is difficult with metals.
- Fatigue Resistance: They can withstand repeated stress and strain without failing, making them ideal for aircraft wings and wind turbine blades.
- Thermal Insulation: Many composites are poor conductors of heat, providing excellent insulation.
5. How do the matrix and reinforcement work together to give a composite its unique strength?
The matrix and reinforcement have a symbiotic relationship. The reinforcement, typically in the form of strong, stiff fibres like carbon or glass, is the primary load-bearing component. However, on its own, it would be brittle and unstable. The matrix is the softer material that surrounds the reinforcement. Its job is to bind the fibres together, protect them from physical and environmental damage, and transfer the stress or load from one fibre to the next. This combination allows the composite to handle tension, compression, and shear forces far better than either component could alone.
6. Why are composites like carbon fibre preferred over metals in high-performance applications like aerospace?
Composites are preferred over traditional metals like aluminium or steel in aerospace for several critical reasons. The most important is the high strength-to-weight ratio, which makes the aircraft lighter and therefore more fuel-efficient. Secondly, composites are highly resistant to fatigue and corrosion, which increases the lifespan of the aircraft and reduces maintenance costs. Lastly, they offer immense design flexibility, allowing engineers to create complex, aerodynamic shapes that improve performance and efficiency, which would be very difficult or impossible to manufacture from a single piece of metal.
7. Is an alloy, like steel, considered a composite material? Why or why not?
No, an alloy is generally not considered a composite material. The key difference lies in the scale of combination. In an alloy like steel, different elements (like iron and carbon) are mixed at an atomic level, forming a new material with a uniform crystalline structure (a solid solution). In a composite, the constituent materials remain physically and chemically distinct at a macroscopic or microscopic level. You can still identify the separate fibres and the matrix, whereas in an alloy, you cannot distinguish the individual original elements visually.
