Statistical Characterization of Fiber-Reinforced Polymer Composite Material Properties for Structural Design

A consistent basis for statistically reducing fiber-reinforced polymer (FRP) composite material property test data for load and resistance factor design (LRFD) of composite structures is developed in this paper. A two-parameter Weibull probability distribution is recommended for modeling both strength and stiffness properties. Consistent with practice for other materials used in structural engineering applications, the 5-percentile value of strength of coupons and components, as well as modulus values, appropriately adjusted for the small size of typical data samples, is recommended for the nominal value of strength for LRFD applications. Statistical uncertainty due to small sample size in the data reduction process is accounted for through the use of a data confidence factor, which is the tolerance limit defined as the 80th percent lower confidence level of the 5-percentile value of the population. With the nominal values so determined, appropriate resistance factors for LRFD-based design codes can be derived and limits for qualification and acceptance criteria for FRP composite structural products can be established.