Evaluation of matrix crack growth in interlaminar toughened quasi-isotropic carbon-fiber reinforced plastic laminates up to the very-high cycle regime by ultrasonic fatigue testing
Yuki Nishi, Atsushi HOSOI, Hiroyuki KAWADA
Abstract
It is time-consuming to conduct conventional hydraulic fatigue testing up to the very-high cycle fatigue (VHCF, N (number of cycles) ≥ 10 8 ) regime. Ultrasonic fatigue testing has been proposed as an accelerated alternative method. In this study, ultrasonic fatigue testing was conducted on interlaminar toughened quasi-isotropic carbon-fiber reinforced plastic (CFRP) laminates to evaluate the characteristics and mechanism of fatigue up to the VHCF regime. Hydraulic fatigue tests were conducted at the same stress ratio as a comparison. The resulting S–N diagrams showed a lower fatigue strength and different fatigue mechanisms for specimens subjected to ultrasonic fatigue tests compared with those subjected to hydraulic fatigue tests . The observed growth of the matrix crack density in each laminate layer was used to perform a shear-lag analysis to calculate the energy release rate considering off-axis matrix cracks . The results suggested different damage growth behaviors for specimens subjected to ultrasonic and conventional fatigue tests .