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Properties of FRP Composites

THe Unique Mechanical Properties of Fiber Reinforced Polymers


A. & F. Michler/Photolibrary/Getty Images

Fiber Reinforced Polymer (FRP) composites are used in a wide variety of applications. Their mechanical properties provide unique benefits to the product they are molded into. FRP composite materials possess superior mechanical properties including:

  • Impact resistance
  • Strength
  • Stiffness
  • Flexibility
  • Ability to carry loads

When designing products out of FRP materials, engineers use sophisticated composite material software which calculates the known properties of given the composite. Typical tests used to measure the mechanical properties of FRP composites include:

  • Shear stiffness
  • Tensile
  • Flexible Modulus
  • Impact

The two major components of an FRP composite material is resin and reinforcement. A cured thremosetting resin with out any reinforcement is glass like in nature and appearance, but often very brittle. By adding a reinforcing fiber such as carbon fiber, glass, or aramid, the properties are vastly improved.

Additionally, with reinforcing fiber, a composite can have anisotropic properties. Meaning, the composite can be engineered to have different properties in different directions depending on the orientation of the fiber reinforcement.

Aluminum, steel, and other metals have isotropic properties, meaning, equal strength in all directions. A composite material, with anisotropic properties, can have additional reinforcement in the direction of stresses, and this can create more efficient structures at lighter weights.

For example, a pultruded rod having all fiberglass reinforcement in the same parallel direction could have tensile strength upwards of 150,000 PSI. Where as a rod with the same area of random chopped fiber would only have tensile strength around 15,000 PSI.

Another difference between FRP composites and metals is the reaction to impact. When metals receive impact, they can yield or dent. While FRP composites have no yield point and will not dent.

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