Mode II interlaminar fracture of hybrid woven carbon-Dyneema composites

Recently, there has been renewed interest in interwoven hybrid composites. Hybridization of different fiber types within composite laminates provides opportunities to extend the design space and optimize properties such as strength and toughness. In this paper, the Mode II fracture behavior of a hybrid carbon-Dyneema fiber-reinforced composite is studied experimentally. The usual linear elastic fracture mechanics (LEFM) methods for measurement of interlaminar toughness are not readily applicable to hybrid composites due to the presence of large fracture process zones and extensive fiber bridging. Continuously increasing R-curves are obtained from standard data reduction approaches, resulting in poor estimates of Mode II interlaminar toughness values. A more general J-integral-based method coupled with digital image correlation technique is proposed here to obtain more consistent and accurate results. Specimens with different intralaminar and interlaminar hybridization schemes are explored, and the delamination process as well as toughening mechanisms is examined through a fractographic analysis.