Method to test the durability of fiber-reinforced polymers based on elastic modulus

Abstract

The performance degradation of fiber-reinforced polymer is often assessed based on the ultimate strength obtained during a destructive test. This method has the advantages of simple operation, clear internal mechanism, and noticeable data variation. However, because fiber-reinforced polymers are composed of high molecular compounds, their properties are influenced by several factors, such as the manufacturing process and composition ratio. Without a unified benchmark, it is difficult to unify destructive test data obtained by different researchers and organizations. In this study, a new test method named SNFT (Same Non-failure FRP Test) is proposed for assessing the durability of fiber-reinforced polymers. SNFT is a testing method in which the same specimen can be repeatedly tested at different aging periods. The rationality of the SNFT method is analyzed using the displacement compatibility between the degraded zone and the undegraded zone. The conversion principle based on the degraded degree between the destructive test and the SNFT method is deduced by calculation. An experimental test was designed to investigate the test conditions and control parameters of the SNFT method. SNFT and synchronous destructive tests on glass fiber–reinforced plastic were carried out under the conditions of wet heat and alkali solution, and the theoretical results were compared and verified with data in the literature. The results show that compared with the traditional durability destructive test method, the SNFT method shows more consistent data and less data fluctuation and incurs a lower test cost. The elastic modulus, adopted as the durability benchmark, can be similar to the test results of traditional destructive test methods and could be transformed based on the transformation relationship proposed in this article. The degradation of fiber-reinforced polymer in different environments is characterized by the variation in elastic modulus measured using the SNFT method. This study provides a theoretical basis for establishing a unified benchmark of durability tests and data and supports the quantitative design of durability.