MIXED-MODE FRACTURE TEST OF CFRP LAMINATES

Mixed-mode (mode I and mode II) interlaminar fracture toughness of unidirectional reinforced and woven carbon fiber-reinforced plastic (CFRP) is evaluated using DCB specimens. A new testing apparatus is made in order to change the ratio of mode I to mode II across a wide range. The fracture toughness value is evaluated based on beam theory, and the deformation of the specimen is analyzed by the finite element method (FEM). The relationship between compliance and crack length obtained in the experiment agrees with the results obtained by FEM. The constant fracture toughness value, Gc, which is independent of crack length, is obtained. Due to the decrease of the G(I)/G(II) ratio, the fracture toughness value increases. It is shown that the role of mode II changes largely due to the change in the ratio of mode I to mode II, though the mode I component maintains a nearly constant value.