Interlaminar Fracture Behavior of Composite Laminates Estimated by Sandwich ENF Test

The ENF testing for interlaminar fracture toughness is the most useful test method to evaluate the interlaminar fracture behavior of UDCF laminate. In this work, the sandwich ENF testing was presented as a new method to evaluate the interlaminar fracture behavior of various laminates, such as AF/AF, GF/GF, CF/GF, CF/AF, and AF/GF. The specimen consisted of a mid layer with a delamination crack to measure its interlaminar fracture behavior and two stiff outer layers to give adequate bending stiffness to the specimen. The sandwich ENF specimen showed good sensitivity to GIIC for laminates of various fiberous compositions. It was also founded that the change in chemical composition of the matrix resin system was effective to improve the interlaminar fracture behavior of UDCF/GFCSM hybrid laminate. As GIIC increased, the crack growth path shifted from UDCF intralayer to the interlaminar zone between UDCF and GFCSM layers.