SummaryDelamination is an important concern in the context of structural behaviour of laminated composite materials. It is known that delamination can diminish the stiffness and the strength of the material and promote structural failure. Delamination onset and growth is governed by interlaminar fracture toughness of the material. Delamination propagation is frequently dominated by mode II fracture; consequently interlaminar fracture characterization under mode II loading is fundamental to accurately predict the susceptibility of the material to delamination. However, there are several problems inherent to the usual tests employed for mode II interlaminar fracture characterization, e.g., unstable crack propagation and difficulties in crack monitoring during propagation.These issues are discussed in section 1.In section 2 the most popular fracture characterization tests in mode II are presented. A brief description of each one is given, with emphasis on the advantages and drawbacks thereof. The application of the classical data reduction schemes to each test is also described in section 2.1. After a succinct bibliographic review it is concluded that the End Notched Flexure (ENF) and End Loaded Split (ELS) tests are the most suitable ones to fracture characterization of composites in mode II. However, the dependence of 2 measured G IIc on the crack length measurements for those tests is emphasized. In order to overcome this serious disadvantage a new data reduction scheme based only on the specimen compliance is proposed in section 2.2. The method is applied with little differences to the ENF and ELS tests and provides a straightforward measurement of G IIc . Moreover, the method also includes the Fracture Process Zone (FPZ) effect, which was verified to be non negligible under mode II loading. In section 2.3 the referred tests were numerically simulated using a cohesive mixed-mode damage model. Appropriate values of critical strain energy release rates in mode I, II and III respectively, were inputted in the model. The main objective was to verify the capacity of the proposed methodology on the replication of the introduced G IIc . Excellent agreement was obtained for the two tests. The ENF test was proposed as the most suitable for the determination of G IIc owing to its simplicity.In section 3 the dynamic fracture characterization is discussed. The difficulties inherent in the conduct of experimental tests execution are highlighted. The determination of the dynamic fracture toughness of composites is useful when dynamic delamination propagation is the predominant failure mode. Several works of different authors are summarized. One of the remarkable points is related to the existence of a crack speed threshold value, below which the dynamic and quasi-static toughness values are similar.The majority of the authors indicate that fracture toughness tends to decrease with increasing crack speed.The main conclusions of this contribution are summarized in section 4.
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