Material characterization on temperature dependency of fatigue stiffness degradation of CFRP laminate manufactured by filament winding using three-point bending test
Topic(s) : Material and Structural Behavior - Simulation & Testing
Co-authors :
Takeshi WATANABE (JAPAN), Ryoma AOKI (JAPAN), Tomohiro YOKOZEKI (JAPAN), Yuta URUSHIYAMA (JAPAN)Abstract :
A performance requirement of a composite high-pressure vessel (COPV) for automobile applications is characterized by low-cycled fatigue due to high ratio of residual burst strength after durability to initial one. In order to achieve further weight reduction of CFRP, it is required that building an analytical method that can predict precisely not only initial burst strength but also residual one after durability. In addition, in order to verify a certification test and to ensure an end-of-life performance of COPV by numerical analysis, it will become necessary to take into account for the effect of environment temperature and loading sequence on fatigue damage inside CFRP.
We have studied a residual strength after fatigue for CFRP in in-plane share direction, which is strongly related with matrix resin cracks and interface fracture between fiber and matrix resin as major dominants of intralaminar fracture. Characterization of stiffness degradation of filament-wounded CFRP during fatigue using three-point bending test and residual strength after fatigue damage were investigated experimentally. And we have also reported a possibility of numerical prediction of residual mechanical property after fatigue by using finite element analysis with material damage models, which were based on Ladeveze’s model for static analysis and dd/dN model for fatigue analysis.[1][2]
In this study, we describe fundamental efforts to realize the extension of numerical analysis method for predicting the effect of environmental temperature on fatigue damage. We understood experimentally the temperature dependency of the stiffness degradation of CFRP in in-plane shear under fatigue loading. A CFRP laminate of [45/-45]2s layup manufactured by filament winding was used for testing. The stiffness degradation under fatigue was evaluated by three-point bending test and under the temperature conditions of room temperature (RT), +85℃ and -40℃. Figure 1 shows the fatigue stiffness degradation under each temperature. The stiffness degradation during fatigue at -40℃ was more likely to occur than at RT and showed more brittle characteristics. On the other hand, The fatigue stiffness degradation at +85℃ is less likely to decrease than at RT and showed tougher one. These results suggest that the temperature dependency of fatigue stiffness degradation strongly influences that of matrix resin fracture.
In addition, the residual strength at residual stiffness of 80% after bending fatigue at each temperature was evaluated by tensile test at RT shown in Table 1. The residual strength at 85℃ and -40℃ decreased by 20% and 16%, respectively, compared to that at RT%. This means that there are differences of damage propagation during fatigue among each temperature, and it is shown that it is important to understand the temperature dependency of the fatigue stiffness degradation of CFRP.
We have studied a residual strength after fatigue for CFRP in in-plane share direction, which is strongly related with matrix resin cracks and interface fracture between fiber and matrix resin as major dominants of intralaminar fracture. Characterization of stiffness degradation of filament-wounded CFRP during fatigue using three-point bending test and residual strength after fatigue damage were investigated experimentally. And we have also reported a possibility of numerical prediction of residual mechanical property after fatigue by using finite element analysis with material damage models, which were based on Ladeveze’s model for static analysis and dd/dN model for fatigue analysis.[1][2]
In this study, we describe fundamental efforts to realize the extension of numerical analysis method for predicting the effect of environmental temperature on fatigue damage. We understood experimentally the temperature dependency of the stiffness degradation of CFRP in in-plane shear under fatigue loading. A CFRP laminate of [45/-45]2s layup manufactured by filament winding was used for testing. The stiffness degradation under fatigue was evaluated by three-point bending test and under the temperature conditions of room temperature (RT), +85℃ and -40℃. Figure 1 shows the fatigue stiffness degradation under each temperature. The stiffness degradation during fatigue at -40℃ was more likely to occur than at RT and showed more brittle characteristics. On the other hand, The fatigue stiffness degradation at +85℃ is less likely to decrease than at RT and showed tougher one. These results suggest that the temperature dependency of fatigue stiffness degradation strongly influences that of matrix resin fracture.
In addition, the residual strength at residual stiffness of 80% after bending fatigue at each temperature was evaluated by tensile test at RT shown in Table 1. The residual strength at 85℃ and -40℃ decreased by 20% and 16%, respectively, compared to that at RT%. This means that there are differences of damage propagation during fatigue among each temperature, and it is shown that it is important to understand the temperature dependency of the fatigue stiffness degradation of CFRP.