Progressive damage analysis based strength envelope method research for composite bolted joints

Considering the present situation that the foundation data for a new T800 composite system adopted in civil aircraft industries are extremely scarce, a progressive damage method (PDA) substituting the tests can reduce the research period and cost significantly. In conjunction with the progressive damage method and the engineering algorithm, a numerical strategy for the strength prediction of multi-bolt joints is presented. In this strategy, the progressive damage analyses of the samples for determine stress concentration relief factors (SCRFs) were carried out to substitute the physical tests. And the strength envelope was constructed. In order to verify the feasibility of the proposed numerical strategy, a bypass-load modified strength envelope method was adopted. The progressive damage analyses of typical ply for stress concentration relief factors were performed and the predictive value of strength was obtained to calculate the stress concentration relief factors. Modified strength envelope of bolted joints bypass-load for typical ply composite was plotted. The failure load of bolted joints was predicted and compared with test results. It can be found that the strength envelope and the ultimate failure loads as well as failure modes of multi-bolt joints based on the numerical strategy agree well with the test results, which provide evidence for the feasibility of the proposed numerical strategy.