Mechanical properties of FRP materials used for composite strengthening are likely to vary between products manufactured in different facilities. To technically assess similar products to confirm approval for use a specifier must obtainactual properties from the plate manufacturer.
Concrete Society Report TR55 defines that ‘Characteristic rather than mean values should be used for design purposes’ when it comes to material properties. The document defines characteristic property as the mean value less 2xStandard deviation, based on a minimum sample size of 8.
Due to production methods, the mean values can vary from batch to batch,even from the same manufacturer, so the characteristic property is a dynamic figure, depending on the variability of the fibre properties used in production and the volume of continuous fibres in a cross section capable of contibuting to the property of that sample. A knowledgable supplier is unlikely to place a characteristic property on a datasheet, due to the dynamic nature of the calculation of that property, and instead is likely to state a minimum.
With the above in mind the specifier, when assessing equivalence of technically similar looking materials, should check with the manufacturers for the latest figures for a product, to obtain up to date characteristic properties. The method of testing, number of and dates of sample tests should be provided to confirm these calculations.
The normally available characteristic properties from manufacturers are tensile strength, modulus of elasticity and elongation at break.
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