Micro-mechanics of failure for fatigue strength prediction of bolted joint structures of carbon fiber reinforced polymer composite

In this paper, the application of theory of micro-mechanics of failure (MMF) is extended to analyze the fatigue progressive failure and predict the strength for the bolted joint structures of carbon fiber reinforced polymer (CFRP) composites. The MMF approach includes the methods of material strength characterization and structure strength prediction for the CFRP structures. The structure strength prediction is realized by developing the user defined material (UMAT) subroutine with Fortran scripts on the ABAQUS platform. The failure mechanism evolution from initial failure to final failure of the bolted joint structures of the UTS50/E51 laminate under the static loading and the fatigue loading are investigated, respectively, in details by using the MMF approach. The experiments under both static and fatigue loading are performed for the bolted joint structures. The predicted strength accuracy of the MMF approach as well as the classical Tsai-Wu and Hashin theories is compared with the experimental results, which shows the MMF approach has the best accuracy. The predicted macro-scale failure appearances of the bolted joint structures under the static tensile loading and the fatigue tensile loading behave as shearing modes. The validation of predicted macro-scale failure appearances is studied by comparing with the tested results.