Fiberglass Engineering
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FRP 101

Is FRP ductile?
    Elastic elongation is the stretching of a material within a range where it will return to its original shape. If a screen door spring is stretched within the elastic limit, it will return to its original length. Plastic elongation is the stretching of a material in a range where it assumes a new shape. If a screen door spring is stretched beyond the elastic limit, it will have a new, longer length than before. Shigley says, “a ductile material will be capable of a relatively large plastic deformation before fracture”. FRP has a high elastic elongation, much higher than most metals, but it is not ductile. When the laminate strength is exceeded, FRP will fracture.
Why are FRP components usually made to an ID rather than to an OD?
    There are two fundamental reasons. First, most CR FRP is typically molded on a mandrel. Therefore, the ID is controlled by the mandrel size, while the OD becomes a function of the ID and the wall thickness. Second, it is convenient to use standard steel components for FRP molds. Steel vessels are made to a given OD; therefore, the FRP made on these steel vessel parts (such as a steel head used as a FRP mold) are ID parts.
Is it possible to make CR FRP abrasion resistant?
    CR FRP can be made very abrasion resistant by the addition of materials such as silica oxide or silicon carbide particles. AR FRP is widely used in such applications as slurry piping in power plants.
Is there a practical way to handle static discharge issues in CR FRP laminates?
    Static discharge can be a very serious concern for ducting, chimney liners, and vessels subjected to dry, windy conditions. Static discharge is very easily addressed by the use of carbon fiber surface veil and/or the addition of graphite power to the laminate. Of course, provisions must be made for grounding the conductive layer(s).
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Saturday December 4, 2021