Fiber reinforced plastic (FRP), also known as fiber reinforced polymer, is in fact a
composite material constituting a polymer matrix blended with certain reinforcing materials, such as fibers. The fibers are generally basalt, carbon, glass or aramid; in certain cases asbestos, wood or paper can also be used.

The Formation of FRPs

Going back to the basics, there are two processes through which a polymer is developed: step-growth polymerization and addition polymerization. Composite plastics are formed when a couple of homogeneous materials possessing different characteristics bond together to produce a final product with the desired mechanical and material properties. These composite materials can be of two types, fiber reinforced and particle reinforced.

Fiber reinforced plastic is that category wherein the mechanical strength and elasticity of the plastics are enhanced through incorporation of fiber materials. The matrix, which is the core material devoid of fiber reinforcement, is hard but comparatively weaker, and must be toughened through the addition of powerful reinforcing fibers or filaments. It is the fiber which is critical in differentiating the parent polymer from the FRP.

Most of these plastics are formed through various molding processes wherein a mold or a tool is used to place the fiber pre-form, constituting dry fiber or fiber containing a specific proportion of resin. After ‘wetting’ dry fibers with resin, “curing” takes place, wherein the fibers and matrix assume the mold’s shape. In this stage, there is occasional application of heat and pressure. The different methods include compression molding, bladder molding, mandrel wrapping, autoclave, filament winding, and wet layup, amongst others.  Check out this video on the process:

Common Properties of FRPs

These composite materials typically exhibit low weight and high strength.  They are so strong that the automotive industry is increasingly interested in using them to replace some of the metal in cars.  Fiber reinforced plastics can be as strong as some metals but they are much lighter and therefore more fuel efficient.

It is possible to customize the properties of fiber reinforced plastics to suit a wide range of requirements. Fiber reinforced polymers typically have impressive electrical and compression properties and display high grade environmental resistance. One important factor that makes these materials a favorite among different industrial sectors is the manufacturing process, which is quite cost-effective. The rate of productivity is medium to high and a ready bonding is exhibited with dissimilar materials.

The other exclusive properties of fiber reinforced plastics include commendable thermal insulation, structural integrity, and fire hardness along with UV radiation stability and resistance to chemicals and other corrosive materials.

The characteristics of fiber reinforced plastics are dependent upon certain factors like mechanical properties of the matrix and fiber, the relative volume of both these components, and the length of the fiber and orientation within the matrix.

Common Fibers include:

  • Glass is a very good insulating material and, when blended with the matrix, forms fiberglass or glass reinforced plastic. Compared to carbon fiber, it is both less strong and rigid and less brittle and expensive.
  • Carbon based fiber reinforced plastics offer high tensile strength, chemical resistance, stiffness, and temperature tolerance along with low thermal expansion and weight.  The carbon atoms form crystals which lie mostly along the fiber’s long axis. This alignment makes the material strong by making the ratio of strength to volume high.
  • Aramid is a fiber component that results in robust and heat-resistant synthetic fibers. It finds wide applications in many industries.

Fiber reinforced plastics find wide applications in the automotive, aerospace, construction and marine sectors. Glass fiber reinforced plastics are a very good option for the power industry as they are devoid of any magnetic field and can offer considerable resistance to electric sparks. The uses are diversifying, a phenomenon evident in the entry of carbon fibers in sports goods, gliders, and fishing rods, along with Japan’s application of FRPs to hydraulic gates.

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