Accelerated testing for long-term strength of innovative CFRP laminates for marine use

Abstract

We have proposed the accelerated testing methodology for the long-term durability of polymer composites based on the time–temperature superposition principle (TTSP) to be held for the viscoelasticity of polymer matrix. In this paper, the prediction of long-term strength of CFRP laminates for innovative marine use under water absorption conditions were performed by our developed accelerated testing methodology. Three kinds of CFRP laminates employed were conventional plain fabric T300 carbon fibers/vinylester, flat yarn plain fabric T700 carbon fibers/vinylester and multi-axial knitted T700 carbon fibers/vinylester for innovative marine use as a lightweight CFRP ship structures. These CFRP laminates were prepared under three water absorption conditions of Dry, Wet and Wet + Dry after molding. The three-point bending constant strain rate (CSR) tests for three kinds of CFRP laminates at three conditions of water absorption were carried out at various temperatures and strain rates. As the results, the master curves of CSR strength for these CFRP laminates at three water absorption conditions are constructed by using the test data based on TTSP. Furthermore, the time–temperature–water absorption superposition principle (TTWSP) hold for the flexural CSR strengths for these CFRP laminates. Therefore, it is possible to predict the long-term strength for these CFRP laminates under an arbitrary temperature and water absorption conditions using the master curves. It is cleared from the master curves that the degradation rate of CSR strength of these CFRP laminates is determined only by increasing of time, temperature and water absorption and is independent upon the type and weave of carbon fibers.