What Are FRPs?

Fiber Reinforced Polymer (FRP) has been used successfully for decades in the aerospace, shipbuilding, and sporting goods industries. They are constructed of fibers (such as glass, carbon, and Kevlar) embedded in a resin matrix. The function of the resin is to protect the fibers and to distribute the loads evenly among them. Various coatings can be added to the fibers for a better bond-to-resin matrix. A major advantage of FRPs compared to other structural materials is their anisotropy, i.e. FRPs have physical properties that are different when measured along different axes or directions. By orienting the fibers in the desired direction, one can achieve the required strength in each direction.

Samples of QuakeWrap® glass and carbon fabric and carbon plates are shown here. Additionally, hybrid fabrics constructed of one or more types of fiber can be ordered. For most civil engineering applications, the fabrics are supplied in rolls that are 50 inches (1.27 m) wide.

In the field, the fabrics are saturated with QuakeBond™ resins to form what is collectively refered to as FRP.

The stress vs. strain relationship for FRPs is often compared to steel rebars. Unlike steel that yields, FRPs behave linearly elastic to failure. While at first this may appear to be a severe shortcoming, as explained under beam and column sections, ductile behavior of the member can be achieved if designed properly. The modulus of elasticity for glass FRPs is about 3,000 ksi and that for carbon is about 9,000 ksi. Stiffer materials are available (such as QuakeWrap® DU50C), but the above values are common for construction-grade FRPs that are produced in the field from fabrics. It is noteworthy that both carbon and glass FRPs are much stronger than steel.