Fatigue Design of Tubular Carbon-Aluminium Bonded Joints Under Constant- and Variable-Amplitude Fatigue

This study investigates the fatigue behaviour of carbon fibre-aluminium adhesively bonded tubular joints, representative of the suspension arm of a Formula SAE racing car, under both constant- and variable-amplitude fatigue loading. A linear elastic stress analysis was conducted using two-dimensional axisymmetric finite element models to determine the singular stress field parameters-specifically the Generalised Stress Intensity Factor (H₀) and the stress singularity exponent (s)-at critical adhesive-adherend interfaces. Experimental tests under quasi-static loading and constant amplitude, as well as variable-amplitude fatigue conditions, were performed. The constant-amplitude fatigue data were reanalysed in terms of both nominal maximum shear stress and H₀. The results show that the scatter index of the fatigue data was reduced by a factor of 1.46 when H₀ was used as the fatigue-driving parameter, indicating an improved correlation of the experimental results. Variable-amplitude fatigue tests were interpreted using Miner's cumulative damage rule, confirming the suitability of H₀-based life estimation models even under realistic, variable-amplitude loading conditions. The results demonstrate that H₀ is an effective parameter for rationalising fatigue performance of tubular bonded joints and highlight its potential for fatigue design in composite-metal structural applications.