超高サイクル疲労におけるクロスプライCFRP積層板のトランスバースクラック発生評価

抄録

Carbon fiber reinforced plastics (CFRPs) are expected to be applied for rotating members such as fan blades of turbofan engines. They are subjected over 108 loading cycles during their operation time, since it is essential to investigate the very high cycle fatigue (VHCF) behavior of CFRPs. To accelerate the test time up to VHCF regime, ultrasonic fatigue testing machine which can apply the specimen ultrasonic load at a frequency of 20 kHz was used. Hydraulic fatigue test was also conducted to evaluate the transverse crack initiation in the high cycle fatigue (HCF) regime and to confirm the consistency of the ultrasonic fatigue test. The S-N diagram showed the linear decrease in HCF regime. On the other hand, the slope of the S-N curve became gentle in the VHCF regime. Furthermore, no cracks occurred in all specimens tested with the initial maximum strain less than εmax=0.193% up to 6.56×109 cycles in maximum.