Introduction

What is FRP?


Fiber Reinforced Polymer (FRP) is comprised of a polymer (such as epoxy, vinyl-ester, or polyester) that is reinforced with a fiber (such as carbon, glass, Kevlar, basalt, etc.); thus the name Fiber Reinforced Polymer or FRP. The fibers are the main source of strength and stiffness in FRP. The resin serves two primary purposes: a) it distributes the load among all fibers, and b) it protects the fibers from environmental effects such as abrasion, etc. 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.

Origins of FRP for structural repair

The original technique of using FRP for repair and retrofit of structures was pioneered in the late 1980s by Professor Ehsani and his associates at the University of Arizona. The technique developed at that time is known today as the wet layup system. In the wet layup system, fabrics of carbon or glass are saturated with epoxy resin in the field and applied to the structure (similar to wallpaper); by the next day when the epoxy cures, the FRP will have a strength about three times that of steel!

For over two decades the construction community continued to use either fabrics in a wet layup application or carbon strips. These materials by nature have limitations and they had prevented structural engineers from offering cost-effective high quality solutions to several applications.

Advantages of FRP in construction

• High tensile strength (3-to-5 times stronger than steel) • Low weight (no foundation adjustments required) • Corrosion resistance and protection • Chemical protection • Waterproof • Rapid repair capability • Versatile • Odorless, non-toxic (QuakeWrap products) • NSF-61 certified for pipes • Minimal investment when compared to complete structural replacement.

Why repair using FRP?

• Increase structural load capacity • Repair deteriorated materials • Repair accidental damage • Correct construction or engineering errors • Comply with existing or new codes • Blast repair • Prevent catastrophic failure Important engineering points for FRP in construction

• The strength of FRP comes from the fiber content, not from the resin • The same fabric can be made into laminates with different thicknesses (by adding more resin) • Because stress is calculated as force divided by cross sectional area, the same fabric can give different stress values.