Determining mode Ⅱ cohesive law of Pinus pinaster by combining the end-notched flexure test with digital image correlation

摘要

This work addresses the direct identification of cohesive law of Pinus pinaster in mode Ⅱ. The end-notched flexure (ENF) test is selected for mode Ⅱ loading. The strain energy release rate in mode Ⅱ (G_II) is determined according to the compliance-based beam method (CBBM) by processing the global load-displacement curve, without requirements to monitor the crack length during test. The fracture test is coupled with digital image correlation (DIC) for the local measurement of the crack tip opening displacement in mode Ⅱ (W_II). Using a direct method, the cohesive law in modeⅡ (σ_II-W_II) is determined by differentiating the G_II-W_II relationship. The procedure is validated from both numerical, using finite element analyses including cohesive zone modelling, and experimental approaches. The methodology and accuracy on this reconstruction is discussed. It is concluded that the proposed data reduction scheme is suitable for assessing the cohesive law of P. pinaster in mode Ⅱ.