Abstract: A hybrid experimental-numerical approach is disclosed to determine the Mixed Mode (I/III) dynamic fracture initiation toughness of engineering materials. Cylindrical Aluminum alloy specimens with a V-notch spiral crack on the surface at spiral angles of 0°, 11.25°, 22.5°, 33.75°, and 45° are subjected to dynamic torsion load using torsional Hopkinson bar apparatus. The torque applied to the specimen at the onset of fracture is measured through strain gages attached to the incident and transmitter bars. A stereo digital image correlation is performed to measure the full-field deformation, and the crack mouth opening displacement as a function of loading time and is used to estimate the time at which the crack initiation is started. The dynamic stress intensity factors are extracted numerically based on the dynamic interaction integral method using Abaqus. The Mode-I (KId), Mode-III (KIIId), and Mixed Mode (K(I/III)d) dynamic initiation toughness is presented as a function of spiral angles and loading rate.