Abstract
Current guidelines stipulate a sample size of five for a tensile coupon test of fiber reinforced polymer (FRP) composites based on the assumption of a normal distribution and a sample coefficient of variation (COV) of 0.058. Increasing studies have validated that a Weibull distribution is more appropriate in characterizing the tensile properties of FRP. However, few efforts have been devoted to sample size evaluation based on a Weibull distribution. It is not clear if the Weibull distribution will result in a more conservative sample size value. In addition, the COV of FRP’s properties can vary from 5% to 15% in practice. In this study, the sample size based on a two-parameter Weibull distribution is compared with that based on a normal distribution. It is revealed that the Weibull distribution results in almost the same sample size as the normal distribution, which means that the sample size based on a normal distribution is applicable. For coupons with COVs varying from 0.05 to 0.20, the sample sizes range from less than 10 to more than 60. The use of only five coupons will lead to a prediction error of material property between 6.2% and 24.8% for COVs varying from 0.05 to 0.20.
Highlights
Fiber reinforced polymer (FRP) composites have been increasingly used in the strengthening of engineering structures due to their advantages of high tensile strength, excellent corrosion resistance, light weight, and flexibility in shape [1,2,3,4,5,6,7]
The results showed that the Weibull distribution had a slight advantage in characterizing the tensile strength of FRP composites [25,30]
This paper presents an analysis on the sample size for FRP coupon test
Summary
Fiber reinforced polymer (FRP) composites have been increasingly used in the strengthening of engineering structures due to their advantages of high tensile strength, excellent corrosion resistance, light weight, and flexibility in shape [1,2,3,4,5,6,7]. Available guidelines stipulate a minimum value of five for FRP tensile coupon test [20,21,22,23] This stipulation uses a normal distribution for the characterization of FRP’s properties, and assumes a value of 0.058 as the sample coefficient of variation (COV) [21]. A normal distribution is assumed in current guidelines for the characterization of FRP’s tensile properties, many studies have revealed that a Weibull distribution is more appropriate as the describing model, especially for the tensile strength [24,25,26,27]. The accuracy of using only five coupons for COVs ranging from 0.5 to 2.0 were analyzed It is expected the sample size analysis will facilitate researchers and engineers in choosing the sample size for FRP tensile test and provide reference for specification in FRP guidelines. This will be beneficial for experiments exposed to severe environments, where the COVs of FRP’s properties may be high [38]
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