Determination of the Interlaminar Fracture Toughness of Glass-Fiber-Reinforced Plastics on Ring Segments

A method is developed which allows one to estimate the fracture toughness G _{I c} of fiber-reinforced plastics using ring segment specimens. It is shown that this method reduces to the so-called angle method. The approach developed was tested on segments of glass-fiber-reinforced plastic (GFRP) rings based on an EDT-10 epoxy matrix and RVMPN 10-1200-14 glass fibers. The crack was set by a polyimide film placed in the specimen midlayer at the winding stage. The ring thickness was 1 to 4.5 mm. The fracture toughness G _{I c} was also calculated from force F-displacement D diagrams. It was found that the values of G _{I c} determined by both methods agreed well. For 2 mm thick segments with long (L 30 mm) cracks, G _{I c} was practically independent of L and , and, for the GFRP examined, it could be regarded as a material constant.