Using the Finite Element Method to Analyze Asymmetric Double Cantilever Beam Specimens

There are several experimental methods documented in the literature in order to determine the mixed mode fracture toughness in laminated composites. In these test methods, the percentage of mode I and II load state at the crack tip are well known and so GI and GII. Nevertheless, the required test fixtures are somewhat complex. ADCB (Asymmetric Double Cantilever Beam) specimens in which the crack plane is out of the laminate midplane, are useful to easily produce a mixed mode load state at the crack tip of the samples. This test configuration is as simple as pure mode I tests. Nevertheless, the mixed mode load state at the crack tip cannot be controlled by means of the test fixtures and then, GI and GII are not easy to be calculated. In this test configuration, the position of the crack plane controls the percentage of mode I and mode II load at the crack tip. In this paper, the finite element method has been used in order to analyze the asymmetric DCB specimen. GI and GII were calculated for different crack plane positions and from these results, an empirical equation was derived.