Comparison on Mode I and Mode II Interlaminar Fracture Toughness of Composite Plates according to Curvature Changes

This paper compared the mode I and mode II interlaminar fracture toughness of composite plates in relation to curvature changes. The curvature was set at R1/1,500 mm, R1/1,700 mm, R1/1,900 mm, and R1/2,100 mm depending on the pressure vessel size, and mode I and mode II tests were conducted on plates with and without curvature. The specimens were DCB and ENF, and the laminate angle was fixed at 0 degrees to minimize angle-related changes. The tests were carried out in accordance with ASTM D5528 and D6671/D6671M. The results showed an increase in interlaminar fracture toughness with increasing curvature for mode I tests, but no difference for mode II. The results of this paper can be used for accurate prediction of progressive failure of pressure vessels and composite structure with curvature.