Study on probability model and length effect of tensile strength of unidirectional CFRP plate

This manuscript investigates the probability model and the length effect of tensile strength for unidirectional plates of carbon fiber reinforced polymers (CFRP). Firstly, 30 unidirectional CFRP plates with length of 250 mm are investigated by tensile strength tests and statistical analysis of strength probability characteristics with Normal, Lognormal, traditional Weibull and couple-Weibull distribution. While the test results show that the probability density curve of tensile strength exhibits double peaks, a couple-Weibull model is proposed to describe the probability characteristics of tensile strength, which exhibits good accuracy and applicability with comparison to the experimental results. On this basis, the tensile strength of ten groups of unidirectional CFRP plates with different lengths is tested. The results show that the influence of length effect on tensile strength is significant, and the maximum strength reduction rate is 17.11%. Finally, a probability model of tensile strength considering length effect is established based on couple-Weibull model. With comparison to the test results, it is validated to properly consider the variation of tensile strength with different lengths for unidirectional CFRP plate and give accurate prediction results.