Prediction of the critical stress intensity factor of single-lap adhesive joints using a coupled ratio method and an analytical model

The ratio method coupled with the analytical Volkersen model is proposed for the prediction of critical stress intensity factor ( H c ) in adhesively bonded single-lap joints. Based on the ratio method, it was shown that despite the singularity of the stress intensity factor ( H) near the bonding end, the ratio of H ( H c ) for two single-lap joints with different substrate thicknesses is almost equal at singular and nonsingular regions. It was also found that for joints with different substrate thicknesses, the ratio of H based on the interface shear stress obtained by finite element method is almost equal to the ratio of H obtained using the Volkersen model based on the shear stress along the adhesive mid-plane. The proposed method was applied on single-lap joints with different substrate thicknesses and bonding lengths. According to the experimental results, it was shown that, despite the considerable errors which exist in the stress prediction using the Volkersen model, a combination of Volkersen model and the ratio method could predict the H c of the tested single-lap joints very well. Also using the obtained H c , failure loads of the tested joints were predicted. A good correlation was found between the experimental data and the theoretical predictions.