Life prediction of composite materials in off-shore application

In this paper, the conventional methods to determine shift factor were analyzed and discussed for its disadvantages in life prediction applications. A programme was developed to determine the shift factor automatically. Furthermore, a new model was proposed for modeling the master curve, showing the relationship of storage modulus with time and temperature, with the consideration of shift factor different below and above glass transition temperature. Epoxy-carbon composite was investigated by dynamic mechanical analysis (DMA) and flexure test. DMA data at different frequencies with the changing of temperature were used to determine the shift factor at different temperatures. The flexure test provided the strength versus failure time at different cross head speeds and different temperatures. The shift factors were obtained by the developed programme and the proposed new model, respectively. The predicted master curves by both methods agree well and the obtained shift factors were applied on flexure strength to predict the strength changing with time. With the proposed new model, the life prediction was established for further investigations.