2017 Volume 43 Issue 5 Pages 193-200
Stitched CFRP, reinforced through the thickness by z-fibers like kevlar and carbon fiber, is expected to be used in the automobile industry. In the previous study, the interlaminar toughness properties evaluations of the stitched CFRP have been made. But, many of those evaluates were in a single mode, and there are few studies about mixed mode. In this study, the mixed-mode interlaminar fracture properties of the stitched CFRP laminates were evaluated, and it is intended to clarify the mode ratio dependence of fracture toughness. The I+II mixed mode interlaminar fracture toughness testing, Mixed mode bending (MMB) testing were performed for the stitched CFRP laminates specimen (reinforced by polyarylate z-fibers) and unstitched specimen. For these MMB testings, the specimens, test apparatus and crack observation devices were designed and produced. The crack growth observations were performed in the mode ratioGI/GII=0.55, 1.0 and 1.8. As a result, the fracture criterion of the stitched CFRP was revealed that was applicable ellipse law, GI is in the major axis and GII is in the minor one, and stitching is not contributed to Mode II fracture suppression.
