Fiber Reinforced Plastics (FRP)

October 13, 2016

Fiber reinforced plastic (FRP) is a composite material that can be used to manufacture products that require great strength, while resisting extreme temperatures and chemical attacks.

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Elevated pipe shoes like the ones pictured above are made from FRP to give them incredible compressive strenth and extreme resistance to a wide range of temperatures and chemical attack.

Fiber-reinforced plastic (FRP) is also known as fiber-reinforced polymer (also FRP) and is a composite material composed of a polymer matrix with fiber reinforcement. Generally, the fibers are glass, carbon, aramid, or basalt. Glass fibers are relatively cheap and offer great insulation. They are often used in the power industry because they have no magnetic field and have a high electrical resistance. Carbon fibers have higher tensile strength, a low thermal expansion coefficient, and a higher chemical resistance than other types of reinforcing fibers.

What is the Matrix?

The polymers are manufactured through either step-growth polymerization or addition polymerization and when chemical additives are introduced to alter the properties of the polymer, it is referred to as a plastic. This is the matrix, and it usually has desirable material properties such as electrical or thermal conductivity or corrosion resistance. However, the matrix generally has much weaker mechanical properties than is required for the situation. For that reason, fibers are introduced to reinforce the matrix and provide additional material strength and elasticity.

FRP Manufacturing

FRPs are manufactured in much the same way as other composites. A mold is used to shape the pre-form. Then, the resins are injected into the system to “wet” the pre-form. After a curing stage in which heat or pressure may be applied, the composite piece will then be removed from the mold and is ready for service.

FRP Strength Properties

The orientation of the reinforcing fibers play an important role in the strength of the final composite material. When the fibers are parallel to the load, the composite is at its strongest, and when the fibers are normal to the load, the composite is at its weakest. In fact, in that case, the composite is weaker than the matrix alone. Therefore, it is critically important that the production process properly orients the reinforcing fibers.

Quality Bonding

However, it is also important for the matrix to meet certain requirements for an appropriate composite material. The matrix must be able to saturate and bond with the reinforcing fibers. Preferably, the matrix should bond chemically instead of physically with the fibers in order to promote maximum adhesion. Also, it is important that the matrix envelop the fibers completely, or they could incur cuts or notches that might reduce their strength.

In general, FRPs can have much higher tensile strengths than a polymer matrix alone while preserving desirable physical properties. However, it is crucial to consider the alignment of the fibers as well as the direction of the load in order to ensure that the reinforcing fibers add strength, instead of reducing it.

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