Axial Tensile Adhesively Bonded Performance of Carbon Fiber Composite Tubes Under Room-Temperature and Low-Temperature Circulation

This study investigated the axial tensile performance of adhesively bonded T700/C204 carbon fiber composite and TC4 titanium alloy tubular single-lap joints under three distinct temperature conditions: room temperature, low temperature (-65 °C), and room-low-room-temperature cycling. Two configurations of adhesively bonded joints-composite-composite and composite-titanium-were tested. Specimens were designed to evaluate the influence of spew-fillet and perfect lap configurations on uniaxial tensile bonding strength across varying temperature environments. Analysis of the final failure morphology, stress concentration locations, ultimate failure loads, and load-displacement curves revealed that stress concentration and peeling stress were most pronounced at the ends of the bonded region, which served as the initiation points for failure. The adhesively bonded joints exhibited two distinct failure modes, strongly correlated with material properties and environmental temperature. The titanium alloy tubular joints predominantly experienced adhesive layer failure, while the carbon fiber three-way tubular joints were primarily characterized by fiber-tear failure. Environmental temperature significantly influenced the strength of the adhesively bonded joints. Specifically, the tensile failure limit of the bonded specimens subjected to low-temperature cycling (25~-65~25 °C) was approximately 61% higher than that observed under the room or low-temperature conditions. Furthermore, the experimental results demonstrated that a maximum failure load of 27.522 kN and a shear strength of 10.956 MPa were achieved. Notably, the presence of adhesive spew-fillet had a negligible impact on the bonding strength of the joints.