Influence of the Mode Mixity Ratio and Test Procedures on the Total Energy Release Rate in Carbon-Epoxy Laminates

AbstractIn this work, the fracture behaviour under modes I, II and different mixed mode I/II ratios has been studied for a AS4/3501-6 carbon fibre epoxy resin laminate. Mixed Mode tests were carried out by means of two different procedures: MMB (Mixed Mode Bending) and ADCB (Asymmetric Double Cantilever Beam). ADCB specimens, 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. The ADCB test is not still covered by international standards, so the calculations were performed by means of the Finite Element Modelling (FEM) and analytical formulation developed in previous works. FEM was used in order to analyze modes I, II and mixed I/II and to compare the experimental and numerical results. It was found a good agreement between ADCB and MMB tests. On the other hand, it was also observed that the critical energy Gc increased as the mode mixity ratio GII/Gc increased. Finally, experimental and numerical results showed a good agreement as the differences obtained from both procedures were generally lower than 10%