Evaluation of mode i interlaminar fracture toughness of filament-wound GFRE composite pipe

A common industrial production process for composites is filament winding, widely used for the production of axially symmetric components. The important interlayer properties cannot be evaluated using available ISO and ASTM standards, because of the curved surfaces and partially interwoven fibres. This paper presents a modified test geometry for measuring the critical energy release rate GIc directly from the real filament wound products. Different specimen geometries were investigated numerically for their stress state at the crack tip and tested experimentally. Results were also compared against flat specimens tested according to ISO/ASTM and made from the same constituent materials as the pipe. Testing specimens taken from real filament wound pipe give more relevant results than making flat specimens especially for fulfilling the test standard´s requirements.