Temperature effect on the dynamic bond behavior of CFRP/steel single-lap shear joints

In this work, CFRP plates were made using vacuum assisted resin transfer molding (VARTM) technique. CFRP/Steel single-lap shear joints were manufactured by bonding steel and CFRP together with epoxy resin. Specimens were tested under dynamic tensile loading (0.625 m/s) on a servo-hydraulic high rate testing system under four temperatures (-25, 0, 50, 100 C). The experimental results showed that the mechanical properties of joints were sensitive to temperature. In a certain range, both the bond strength and interfacial fracture energy of specimens increased from -25 to 50 C. When the temperature exceeded the glass transition temperature of the adhesive, bond strength and interfacial fracture energy decreased significantly. The failure modes of specimens were different at varying temperatures. At the low temperature (-25 C and 0 C), the failure mode of joints were adhesive/steel interface debonding failure. At the temperature of 50 C, the failure mode turned to the mixed failure. When the temperature reached 100 C, the failure mode changed to adhesive/CFRP interface debonding failure. Moreover, the strain field distribution of FRP in overlapping area at different temperatures was analyzed using a digital image correlation (DIC) method. The results showed that the strains of FRP at the edge of overlapping area were larger than those in the center, and final failure was initiated at the edge of the specimen.