A progressive damage analysis based characteristic length method for multi-bolt composite joints

A progressive damage analysis based characteristic length method (PDA-based CLM) with only unidirectional layer properties required is proposed to predict the failure of composite multi-bolt joints. This method absorbs the convenience of the CLM on predicting failure of multi-bolt joints and introduces the PDA to obtain the characteristic lengths, which avoids time-consuming and expensive characteristic length tests. Meanwhile, only two simple and universal structures, an open-hole laminate and a single-bolt joint, instead of complex multi-bolt joints, are conducted by the PDA, which provides positive advantages for prediction accuracies and escapes from unbearable time consumption due to large amount of numerical iterations. Two progressive damage models (PDMs) which are composed by in situ strength, Hashin or modified Yamada–Sun criterion and Camanho’s degradation rules are recommended. Static tensile tests of multi-bolt joints were also carried out. Although the final failure load errors of multi-bolt joints predicted by the method proposed are over-conservative, further schematically designed error transfer analysis discloses the errors are mainly caused by the CLM itself. In fact, the errors induced by the numerical characteristic lengths are no more than 4%, which suggests a good prospect of the proposed method in engineering.