Experiments are carried out to determine the delamination toughness for a crack along the interface between two transversely isotropic materials. The material chosen for study consists of carbon fibers embedded within an epoxy matrix. A crack is introduced between two layers of this material, with fibers in the upper layer along the +45
-direction and those in the lower layer along the −45
-direction both with respect to the crack plane. The Brazilian disk specimen is employed in the testing.