The effects of loading rate on the crack growth behavior of adhesively bonded carbon fiber reinforced plastic (CFRP) joints were investigated. The split Hopkinson pressure bar (SHPB) apparatus and the digital image correlation (DIC) technique were employed to obtain the mode I fracture toughness of adhesively bonded CFRP joints during crack propagation. The fracture toughness of titanium alloy adhesively bonded joints was also obtained for comparison. The effect of bending vibration caused by inertial force was suppressed by controlling the incident wave of the SHPB apparatus in the impact test. In addition, the strain based evaluation formula was used for the fracture toughness tests in order to improve the accuracy of the fracture toughness evaluation. The fracture toughness of the CFRP adhesively bonded joints slightly increased as loading rate increased at the onset of crack growth. However, it slightly decreased during crack propagation with increasing loading rate for the loading rate of less than 1.67 × 10-2m/s and it increased for the loading rate of greater than 1.67 × 10-2m/s. The loading rate dependence of the titanium alloy adhesively bonded joints did not appear both at the onset of crack growth and during crack propagation. The fracture toughness of the CFRP adhesively bonded joints was higher than those of the titanium alloy adhesively bonded joints regardless of loading rate.
