Fracture Modes of Oriented Polypropylene

This paper describes the fracture modes of both notched and unnotched polypropylene which has been oriented with a solid phase roll-drawing process. The shear strength of the unnotched material is estimated with a single off-axis tensile test. The notched specimens, when stressed in the roll-drawn direction, fractured normal to the fibrous structure and with a brittle mode. This brittleness enables a K _Ic to be reported. The inapplicability of linear elastic fracture mechanics at other angles of loading is also iden tified.