The fatigue characteristics of carbon fiber reinforced plastics (CFRPs) in the very high cycle fatigue (VHCF) regime have not been well understood. Moreover, it is necessary to research the fatigue behavior of L-shaped CFRP laminates in VHCF regime, which is often seen in structures. To investigate the fatigue behavior of L-shaped CFRP laminates in the VHCF regime, an ultrasonic fatigue test method was constructed in this study. An ultrasonic fatigue test was conducted in the range of 107 - 109 cycles. The working frequency was 20 kHz, and the geometry of the specimen was designed by the results of finite element analysis to resonate in the same frequency. Displacement, temperature, and fatigue damage of specimen were observed. As a result, it was confirmed that specimens resonated at 20 kHz during the test. The high temperature was measured, and delamination was observed at the curved section of specimens. The results showed ultrasonic fatigue tests can perform with L-shaped CFRP laminates. The observation suggests that stress concentration occurs at curved section during the test, and the interlayer stresses between 90°ply and 45°ply near the center of the 16 layers are dominant in fatigue damage initiation.
