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.

The original technique of use of FRP for repair and retrofit of structures was pioneered in the late 1980s by Professor Ehsani and his associates at the University of Arizona. That technique used at that time is what is known 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 the fabrics in a wet lay-up 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.

In 2009, Professor Ehsani introduced the next generation of FRP products called SuperLaminates that overcome the shortcomings of the above mentioned wet layup and narrow carbon strips. As discussed below, these products make many applications that have challenged the engineering and construction professionals for decades possible. In some cases, the solutions would not have been possible without the development of super laminates.

SuperLaminates are constructed with specially designed equipment. Sheets of carbon or glass fabric up to 60 inches (1.5m) wide are saturated with resin and passed through a press that applies uniform heat and pressure to produce the laminate. SuperLaminates shown below offer three major advantages over conventional laminates. First, by using unidirectional or biaxial fabrics, the laminate may provide strength in both longitudinal and transverse directions. This is a tremendous advantage that opens the door to many new applications. Secondly, they are much thinner than conventional laminate strips; with a typical thickness of 0.025 inches (0.66 mm), they can be easily coiled into a circle with a diameter of 12 inches (300 mm) or smaller. Lastly, the number and pattern of the layers of fabrics can be adjusted to produce an endless array of customized products that can significantly save construction time and money.

The figure below shows a 3 ft. wide roll of carbon and a 4 ft. wide roll of glass SuperLaminate next to a conventional 3 inch wide carbon strip. The flexibility of the SuperLaminate is demonstrated in he photograph by coiling it in approximately 8-inch (200mm) diameters and by easily folding a corner of the large carbon panel. SuperLaminates can be produced with highest quality control under ISO 9001 certification; this offers a leapfrog advance in wider acceptance of FRP products in construction projects.

Some of the construction challenges that can be uniquely addressed with super laminates are shown in the links below: described below: