Delamination Mechanism of Multidirectional Reinforced CF/Epoxy Composites

Abstract

The unidirectional CFRP has a weak point in interlaminar strength and therefore, delamination resistance has been evaluated on many types of unidirectional composites and the evaluation method is now being established. In these studies, however, unidirectional reinforced CFRP, in which the stacking sequence is [0]_n, was used. Thus, the measured delamination resistance is not applicable to evaluate the delamination resistance of actual composite structures made from multidirectionally reinforced CFRP. Moreover, the delamination micromechanism of the multidirectionally reinforced CFRP has not been understood yet. Therefore, the material design to improve the delamination resistance of the actual composite structures has not been conducted. In this study, the objective was to examine the delamination resistance curves of multidirectional reinforced CF/Epoxy composites and to investigate problems on the testing method. Additionally, the micromechanism was modeled based on the observations by a scanning acoustic microscope and a scanning electron microscope. As the results, it was shown that the delamination crack propagating between 90° laminae has the highest resistance, and the crack deflection and branching are most effective for increasing the delamination resistance.