FRP Composite 101

FRPs are composites made of a combination of fibre infused in a polymer matrix. Materials used as fibres in FRP composites include glass fibre, carbon fibre, aramids, and natural fibres. Composites have revolutionised material science and engineering in the last few decades. Many industries have incorporated these materials with materials used as fibres in FRP composites such as glass fibre, Kevlar, carbon fibre, and recycled plastics, widely available at low cost. Because of their high strength-to-weight ratio, resistance to corrosion, and ease of use, FRPs are replacing traditional materials such as steel, aluminium, and reinforced concrete across different industries. 

FRP Composite Materials  

FRP stands for Fibre-Reinforced Polymer, a generic name for a class of composite materials. A composite is a material made up of two or more constituent materials with widely different strengths and material properties. Individually each component of a composite lacks the desired property of the other. However, when combined, the resulting composite will have superior material properties compared to the two. 

Components of Composites 

1. Fibres 

There is a range of materials used as fibres in FRP composites. The most common ones include glass fibre and carbon fibre. Other materials such as Kevlar, cloth, and aramid are also used. The choice of fibre largely determines the material properties of the composite. Different fibre materials give various levels of stiffness and tensile strength in the composite. Names of composites also depend on the type of fibre used, for example, GFRP stands for Glass Fibre-Reinforced Polymer, and CFRP stands for Carbon Fibre-Reinforced Polymer. 

2. Matrices 

A matrix is usually a polymer substance that is more elastic than fibre. The matrix is always a thermosetting polymer, and the most common materials used as polymers in FRP composites are epoxies and vinyl esters.

Properties of FRP Composite Materials  

In an FRP composite, the fibre part usually brings most of the strength to the material. The role of the matrix is to encase the fibres and distribute the forces among the fibres. Glass fibre, for example, is stronger than steel for its weight but comes mostly as woven cloth or fibre mats. The resulting glass fibre composite is lightweight, stiff, and strong when combined with epoxy resin. 

Some of the most important properties of FRP composites include:

• Extremely lightweight

• High tensile strength 

• Resistance to water and corrosion

• Resistance to electrical conductivity

• Resistance to chemical substances

• Stability under UV

Applications of FRP Composites  

FRP composites are used to make a wide range of materials, such as: 

• Structural components in the aerospace industry 

• Structural components in the construction industry 

• Body panels for vehicles to reduce weight 

• Electrical insulation components 

• Protective equipment 

• Agricultural equipment 

• Consumer goods 

Manufacturing of FRP Composite Material  

Depending on the type of component being made, the manufacturing of FRP composite material involves the following processes: 

• Pultrusion: This process is used to manufacture FRP composites with a uniform and consistent shape, such as bars, beams, and rods. The fibres are saturated with resin and pulled through a heated steel die, forming it into the desired shape. 

• Filament winding: This process is mostly used to manufacture components such as tanks and pipes. Long filaments of fibre saturated with resin are wound around a mold to produce the desired shape. 

• Hand Lamination: Hand lamination is a low cost method used to manufacture complicated shapes such as the fuselage of aircraft and boat hulls. The fibres cloth is placed over a mould and later saturated with resin. 

• Vacuum Infusion: Vacuum infusion is used to produce extremely lightweight FRP components. FRP component with resin and fibre are placed inside vacuum bags to achieve higher resin penetration into the fibre cloth. 

Benefits of FRP Composites 

• FRPs are extremely lightweight. They are about 1/5th of the density of steel. Aerospace-grade FRPs also have tensile, compression, and flexural strength, making them ideal for aircraft and rocket components. 

• FRPs are highly versatile. Complicated shapes and structures can be easily manufactured using low cost processes. 

• FRP fibre and polymers can be specifically selected to give the composite any desired material property. 

Disadvantages of FRP Composites 

• FRP materials have poor structural strength under elevated temperatures. Most epoxies start losing strength after 60 degrees Celsius. 

• FRP cannot be recycled as they are thermosetting plastics. Disposing of worn out FRP products at an industrial scale can pollute the environment. 

• FRP is more susceptible to ageing as repeated exposure to the elements, or different corrosive substances can cause long-term degradation. 

Conclusion 

Fibre-Reinforced Polymer composites use more than one material bonded together to create a composite that has superior material properties. They tend to be lightweight and suitable for applications to replace conventional materials like steel, aluminium, and plastic. The materials used as fibres in FRP composites can include fibreglass, carbon fibre, cloth, recycled plastics, or other natural fibres that are environmentally friendly. The materials used as polymers in FRP composites are usually thermosetting polymers such as epoxies and vinyl esters.