Mixed mode fracture toughness: An empirical formulation for determination in asymmetric DCB specimens

• Published in: Engineering structures 2010-11, Vol.32 (11), p.3699-3703
• Main Authors: Mollón, V., Bonhomme, J., Viña, J., Argüelles, A.
• Format: Article
• Language: English
• Subjects: Asymmetry; Empirical analysis; Finite element method; Fracture mechanics; Mathematical analysis; Mathematical models; Planes
• ISSN: 0141-0296
• DOI: 10.1016/j.engstruct.2010.08.014

Asymmetric DCB specimens (ADCB), in which the crack plane is out of the laminate midplane, are simple and useful test configurations to produce a mixed mode load state at the crack tip of the samples. This test configuration is as simple as pure mode I tests. However, the analytical procedures developed in the ASTM D5528-01 standard to calculate [inline image] are no longer valid to analyze the ADCB specimen. In this test configuration, the position of the crack plane controls the mode I and modeEEE load levels at the crack tip. In this work an empirical formulation, based on Finite Element Modelling (FEM), has been developed in order to calculate [inline image] and [inline image] (where [inline image]) in ADCB specimens. On the other hand, the Modified Beam Theory (MBT) has been adapted by means of experimental calibration to allow the calculation of G for this test configuration. These formulations have been validated by means of FE modelling for different crack plane positions. Finally, the formulations developed in this paper were used to calculate [inline image] and [inline image] in experimental results on glass fibre epoxy laminates and the obtained results were compared with formulations developed by other authors. A good agreement was found among the different analytical, empirical, and numerical methods studied in this paper.