Effects of fiber orientation and specimen width on delamination fatigue crack growth in CFRP laminates
Nakai Yoshikazu; Fujiwara Muneyoshi; Han Jiyi
Abstract:Constant DG tests were conducted to examine the effects of specimen width and fiber orientation on the Mode I delamination fatigue crack growth behavior of CFRP laminates. For every specimen width, the crack growth rate was lower for the larger angle of crack tip fiber orientation. For the lower angle of crack tip fiber orientation, the growth rate was higher for the wider specimen, while the rate was lower for the wider specimen for higher crack tip fiber orientation. From the microscopic observation by scanning electron microscopy, branching of crack tip, winding of crack path, and bridging of crack faces by fibers were found to be responsible for the effect of fiber orientation. The miss-arrangement of fibers and the anti-plane deformation by Poisson's effect may bring the effect of specimen width. The delamination fatigue crack growth rate for the unidirectional specimen wider than 10 mm gave the upper limit value among every crack tip fiber orientation and specimen width. Key Words:delamination, fatigue crack growth, fiber orientation, specimen width, CFRP lamoinate, constant DG