An experimental study is done on the interlaminar fracture toughness of GFRP (Glass/Polyester) and CFRP (Carbon/Epoxy) satin woven fabric composites. Both fracture toughnesses G_Ic and G_IIc are measured by the use of DCB (Double Cantilever Beam) and ENF (End Notched Flexure) specimens, respectively. The fracture toughnesses in thread and wart direc-tions are also measured to study its dependency on the direction of the crack propagation. As expected, G_IIc is found higher than G_Ic for both GFRP and CFRP. The DCB experiment shows that the fracture toughness G_Ic to initiate the crack propagation is much higher than the dynamic one during the unstable crack propagation. So, unstable crack propagations are observed once the crack starts to propagate until the energy release rate drops significantly due to its propagation under the condition of constant deflection. Both G_Ic and G_IIc are found to depend on the direction of the crack propagation (parallel or transverse to thread direction).