Fiber Structures In Reinforced Composites

In composites, verious kinds of orientations and shapes are used as reinforcement phase. You know that the reinforcement phase is very important to obtain desired strength and other mechanical properties for composite materials. Fiber structures are very important reinforcement phase structures in composite materials. In here, we will explain the general properties of fiber reinforcing agents in composites.

What Is Fiber Reinforcement Used In Composites?

Concrete columns in buildings are fiber-reinforced composites.

Fibers in composite materials are generally produced in very thin filament form. In general applications of composite materials, fibers are produced in diameters ranging from 0.0025mm to 0.13mm. The mechanical strength enhancement of composite materials is very straightforward. Especially in tensile reinforcement in composite materials, fibers are very vital.

In general mechanics of materials, filament form of a material is much more stronger than their bulk form. And also with the reducing daimeter of filaments, tensile strength of material increases. Because of this fact, filament shapes of materials which are called ‘fibers’ are used in reinforcement of composite materials.

Continuous and discontinuous fibers are also avaliable in composite applications. In theory, continuous fibers are possible, but production of them is very hard. So, discontinous fibers are also an application of fibers in composites. For discontinuous fibers, L/D ratio can be around 100. ‘Whiskers’ is an example for discontinuous fibers which has hari-like structure and very low diameter which is around 0.001 mm. This means that, they are superior in applications that tensile stress is prominent.

In general applications, the diameter of used fibers start from 0.0025mm to 0.13mm.

Reinforcement Application Types Of Fibers

Three types of reinforcement applications for fiber reinforcements in composites. The first one is ‘one dimensional reinforcement’ that fibers are oriented in tensile stress application direction. So reinforcement for this condition is provided by fiber reinforcement. Matrix of composite material transmits the stress on fiber reinforcement to overcome this tensile stress.

Three types of fiber reinforcements(Src:Fundamentals ofmodern manufacturing).

The second type of reinforcement is ‘planar reinforcement’ in which reinforcement with fibers is accomplished in two dimensional plane. Conside about the two dimensional tensile stress application on these composites. Planar fiber reinforcement probably overcome this stresses.

The third one is ‘three dimensional reinforcement’ that fiber design in these kinds of composites is accomplished to overcoma three dimensional tensile stress applications.

What Kinds Of Materials Are Used As Fiber Reinforcements?

Wide variety of materials are used as fiber reinforcements in composite materials. But material type also can change according to the matrix material that is used in composite material. These materials are generally used in fiber reinforcements;

  • Metal Fibers: Some metals are very good in tensile strength. So these metals are used as both continuous and discontinuous fibers in composite materials.
  • Boron Fibers: Boron has very good modulus of elasticity value, but high in cost. Composite materials that are produced with boron fiber reinforcements has very good strength/weigth ratio. But, they are used in aircraft and aerospace applications because of their high cost.
  • Carbon Fibers: Along with its very good stifness, low thermal expansion and low density properties are very attractive for carbon fiber reinforced composites. Graphite and amorphous carbon are used generally for carbon fiber reinforcements.
  • Ceramic Fibers: Low density and modulus metals are reinforced with ceramic fibers. Silicon Carbide(Sic) and aluminum oxide(Al2O3) types of ceramics are used as fiber reinforcements.
  • Glass Fibers(Fiberglass): Glass is the most used material as fiber reinforcement in composite materials. E-glass and S-glass are used in fiber reinforcement applications. S-Glass is an expensive glass fiber reinforcement, but its tensile strength and modulus elasticity is best around other fiber materials. E-Glass is strong and low cost but its mechanical properties are lower then other fiber materials.
Fiber-glass fabric.
  • Kevlar 49: It is a special polymer fiber reinforcement material. Density of Kevlar 49 is low and best strength-to-weigth ratio composite are produced with this fiber material.

Fiber reinforcement is vert important are in composite design. It has very specific technique and you can develope yourself in this area.

This can be the general explanation of fiber reinforcement in composite materials. Do not forget to leave your comments and questions about fiber-reinforced composite materials and their features below. Your precious feedbacks are very important for us.

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