Effect of temperature on the mechanical properties of adhesively bonded basalt FRP-aluminum alloy joints in the automotive industry

Abstract

To study the effect of temperature on the mechanical properties of adhesively bonded basalt FRP-aluminum alloy joints (BFRP-Al joints), the two-component epoxy adhesive Araldite® 2015 was selected to fabricate bulk tensile specimens, butt joints (BJs), scarf joints (SJs) with angles of 45° and thick adherend shear joints (TASJs), which were tested at − 40, − 10, RT (25 °C), 50 and 80 °C using a universal testing machine. A differential scanning calorimetry (DSC) analysis of Araldite® 2015 and BFRP was performed, and the strain of bulk specimens at different temperatures was obtained by the 3D digital image correlation (DIC) method. The results show that as temperature increases, the Young's modulus and tensile strength of Araldite® 2015 decrease. Additionally, the tensile strain increases and the mechanical properties change significantly as the glass transition temperature (Tg) is approached or exceeded. The failure strength of BFRP-Al joints at different temperatures is influenced by the performance of the adhesive and the BFRP, and the strength decreases at elevated temperatures. The shear load capacity of BFRP-Al joints is the highest, and the joints are more likely to fail under the normal stress state and combined shear and normal stress state. BFRP damage tends to occur when the joint is subjected to normal stress or low temperatures. It is noted that the failure criteria of adhesively bonded BFRP-Al joints accord with stress criteria under test temperatures. The equation of stress failure criterion at any temperature (from − 40°C to 80 °C) is established to provide a more comprehensive reference for the application of adhesively bonded BFRP-Al joints in automobile industry.