Dependence of Intralaminar Fracture Toughness on Direction of Crack Propagation in Unidirectional Composites

Mode I intralaminar fracture toughness GIC of graphite fiber-reinforced bismaleimide (X5260/G40-800) has been studied experimentally using double edge notch (DEN) specimens and three-point-bend specimens. The intralaminar fracture toughness was found to depend significantly on the direction of fracture propagation. Examination of the fracture surface showed the fracture surface to be relatively smooth or ragged depending on the direction of the fracture propagation, thus substantiating the measured differences in of graphite fiber-reinforced bismaleimide (X5260/G40-800) has been studied experimentally using double edge notch (DEN) specimens and three-point-bend specimens. The intralaminar fracture toughness was found to depend significantly on the direction of fracture propagation. Examination of the fracture surface showed the fracture surface to be relatively smooth or ragged depending on the direction of the fracture propagation, thus substantiating the measured differences in GIC. Furthermore the material exhibited a substantial. Furthermore the material exhibited a substantial R-curve behavior, which appeared related to fiber pull-out.