Coupled continuum damage mechanics and failure envelope method for failure prediction of composite multi-bolt joints

A numerical strategy, based on continuum damage mechanics and the failure envelope method, is proposed for failure prediction of composite multi-bolt joints. First, the design parameters of the failure envelope are determined by virtual tests of simple structures. Then, a modified failure envelope incorporating the bending effect is constructed. Finally, different bearing-to-bypass stress ratios and the influence of bolt rows on the bending effect are discussed. It is shown that the failure envelope with constant bearing-to-bypass stress ratio, obtained by assuming uniform bolt load distribution, is recommended. And the bending effect of single-lap, composite multi-bolt joints is alleviated by the introduction of more bolt rows. These results indicate that failure prediction of composite multi-bolt joints, using the proposed numerical strategy, exhibits excellent agreement with the experimental outcomes. This demonstrates that the numerical strategy is feasible.