Study on mode-I fracture toughness of composite laminates with curved plies applied by automated fiber placement

Interlaminar fracture toughness is an important parameter to characterize the delamination performance of carbon fiber-reinforced epoxy laminates. In this study, the mode-I fracture toughness of interlaminar interfaces with different local ply angles were studied by experiments and numerical simulations. A set of double cantilever beam specimens of T800 carbon fiber/EH104 epoxy were prepared according to the ASTM-D5528–01 standard, where four specimens had straight ply interfaces (0°//0°, 15°//−15°, 30°//−30°, and 45°//−45°) and two specimens had curved ply interfaces (curvature radius: 300 and 500 mm). The mode-I fracture toughness was characterized using a data reduction scheme based on the modified beam theory. The results revealed that the mode-I fracture toughness values for the specimens with a curved ply interface were significantly higher than those for specimens with a straight ply interface.