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FRP 101
What is the typical construction of a CR FRP laminate?
A CR FRP laminate consists of three lamina. Each lamina will be composed of one or more layers.
Surface Veil – This is a resin rich lamina consisting of one or two layers of surface veil. Typically, three types of veil are used: C-glass, polyester and carbon veil.
Corrosion Barrier Interior Lamina – Following the surface veil is a minimum of two 1-1/2 oz/sq ft (450 g/sq m) chopped strand glass reinforced plies. For very aggressive conditions, more plies may be specified.
Structure – Various lamina compositions are used for the structural lamina. The most common ones are filament wound and chop-woven contact molded.
What determines the mechanical properties of FRP?
The mechanical properties of FRP are determined largely by the glass fiber reinforcement scheme used in the laminate. The experienced FRP design engineer tailors these properties to the particular application. Laminate moduli, Poisson’s ratios, coefficients of thermal expansion and density may be calculated using Lamination Analysis software. In some cases, laminate strengths can be predicted using the Lower Bound Method. In other cases strengths must be measured by laboratory test.
Why is FRP Non-Isotropic?
FRP laminates are non-isotropic because of the glass fibers. A common example of a non-isotropic material is wood. In-grain and cross-grain properties of wood are very different. Plywood is made using oriented layers to create a product with tailored properties. In the same way, FRP laminates are often composed of different layers to create the desired global properties.
In general, what are the properties of CR FRP?
CR FRP has a high strength to weight ratio and a relatively low stiffness (modulus) to weight ratio. Laminate strengths can range from 9,000 psi to 90,000 psi in the load bearing direction. Laminate moduli can range from 800,000 psi to 5,000,000 psi, once again in the load bearing direction. By contrast, plain carbon steel has a strength of about 36,000 psi and a modulus of 29,000,000 psi. While many FRP laminates are stronger than steel, all are much less stiff than steel. This results in FRP having a much higher elastic elongation than steel which is one reason FRP is widely used in such applications as fishing rods.
