In order to measure the opening-mode interlaminar fracture toughness of interply hybrid composites, double cantilever beam specimens with three different types of stacking sequence have been utilized in this work. Finite-element analysis combined with a modified crack closure integral has been applied to separate the different components of the strain-energy release rate. In addition to the finite-element method, the method of compliance calibration was used to calculate G C values. Furthermore, the effects of geometrical non-linearity, crack length, specimen width, and number of glass fiber plies were also studied. The results show that crack growth in the three types of specimens is dominated by the opening-mode and the Mode I interlaminar fracture toughness can be approximated. For hybrid composite specimens, the effect of geometrical non-linearity should be included. To obtain stable values of strain-energy release rate the specimen width needs to be carefully chosen while the fracture toughness does not change with the growth of the crack.