Giga-cycle fatigue properties of transverse crack initiation in cross-ply CFRP laminates using ultrasonic fatigue testing

Paper:

icaf2023 Tracking Number 83
PPT: not available

Hosoi Atsushi
Affiliation: Department of Applied Mechanics and Aerospace Engineering, Kagami Memorial Research Institute for Materials Science and Technology, Waseda University, Japan
Shinji Ito
Affiliation: Department of Applied Mechanics and Aerospace Engineering, Kagami Memorial Research Institute for Materials Science and Technology, Waseda University, Japan
Tsuyoshi Miyakoshi
Affiliation: Department of Applied Mechanics and Aerospace Engineering, Kagami Memorial Research Institute for Materials Science and Technology, Waseda University, Japan
Shima Momoka
Affiliation: Department of Applied Mechanics and Aerospace Engineering, Kagami Memorial Research Institute for Materials Science and Technology, Waseda University, Japan
Yuki Nishi
Affiliation: Department of Applied Mechanics and Aerospace Engineering, Kagami Memorial Research Institute for Materials Science and Technology, Waseda University, Japan
Hikaru Saito
Affiliation: Department of Applied Mechanics and Aerospace Engineering, Kagami Memorial Research Institute for Materials Science and Technology, Waseda University, Japan
Hiroyuki Kawada
Affiliation: Department of Applied Mechanics and Aerospace Engineering, Kagami Memorial Research Institute for Materials Science and Technology, Waseda University, Japan

Abstract:

An application of carbon fiber reinforced plastic (CFRP) laminates is being expanded to rotating components such as jet engine fan blades. Since the blade members are subjected to cyclic loading exceeding 10E9 cycles during their design life, it is important to clarify the gigacycle fatigue properties of CFRP laminates and their fracture mechanisms. Thus, the objective of this study was to evaluate the gigacycle fatigue properties of CFRP laminates in transverse crack initiation. A conventional hydraulic fatigue test is too time-consuming, and accelerated tests must be conducted to evaluate gigacycle fatigue properties. In this study, accelerated fatigue tests were conducted at a test frequency of 20 kHz by ultrasonic fatigue testing. The temperature rise of the specimens due to self-heating was prevented by air cooling with dry air and intermittent operation. Therefore, the apparent test frequency was approximately 1.8 kHz. So far, no definite fatigue limit of CFRP laminates has been confirmed. It is known that the initial damage in fatigue of CFRP laminates is transverse cracks, and that its growth and increase can lead to major damage such as delamination and fiber breakage. It is possible to obtain the initial fatigue properties before macroscopic damage occurs by evaluating the initiation life of transverse cracks. In addition, a mechanical model based on a variational approach was proposed for a cross-ply laminates with transverse cracks resonated in the first-order mode by ultrasonic vibration. In this study, [0/906]s cross ply CFRP laminates were used, and the fatigue test was conducted at a stress ratio of R = -1 by the hydraulic fatigue and the ultrasonic fatigue testing. The experimental results showed that no transverse crack initiation occurred in the giga-cycle region, suggesting the existence of the fatigue limit. The stress analysis results of the proposed model showed good agreement with the results of the finite element analysis.