Experimental and analytical approach for the size effect on the fiber strength of CFRP

In this article, experimental test and an analytical approach were conducted to verify the fiber tensile strength of filament wound pressure vessel. As a test method, improved hoop ring test method was considered. From a series of fully scaled hoop ring tests, the size effect showed the clearly observed tendency toward fiber strength degradation with increasing stressed volume. As an analytical method, Weibull weakest link model and the sequential multistep failure model (SMFM) were considered and compared with the test data from hoop ring test and unidirectional specimens test. It was found that the Weibull weakest link model and the SMFM significantly overestimate the size effect on fiber strength. Thus, the fiber strength showed much lower values than those of test data. In this study, an improved SMFM was proposed by considering a modification of the length size effect. Because this model enhances the accuracy of predicting the fiber strength, the fiber strengths from the improved SMFM showed good agreement with the test data.POLYM. COMPOS., 2013.