Temperature effect on the bond behavior of basalt FRP-steel single-lap joints under dynamic tensile loading

In the present work, basalt FRP/steel single-lap joints were tested at various temperatures under dynamic tensile loading. Basalt FRP was fabricated by means of vacuum-assisted resin transfer molding (VARTM) processing, and bonded to steel plates with an overlap length of 25 mm using two-component epoxy resin (Sikadur® 330). Dynamic tensile tests of the BFRP-steel specimens at varying temperatures ranging from -25 to 100 °C were conducted using a servo-hydraulic high-rate testing machine at a loading speed of 0.625 m/s. The deformation and failure behavior of samples in the overlap region were captured using a Phantom v7.3 high speed digital camera at a sampling rate of 20000 fps, and subsequently analyzed using digital image correlation (DIC) method. Experimental results include average bond strength, toughness, bond-slip curves and FRP strain distribution were presented. The average bond strength and toughness increased in the range of -25 to 50 °C, while decreased significantly from 50 to 100 °C as the temperature exceeded the glass transition temperature T_g. The observed typical failure mode in most specimens at low temperature was debonding at adhesive-steel interface, whereas samples ruptured at the adhesive-FRP interface at elevated temperature with lower bearing capacity.