Effect of voids on fatigue damage propagation in 3D5D braided composites revealed via automated algorithms using X-ray computed tomography

The main objective of this study is to analyze the effect of voids on damage evolution in three-dimensional five directional (3D5D) braided composites under fatigue loading. This was achieved by the combination of Micro-CT and novel image algorithms during the interruptive fatigue tests. The present methodology enables the automatic capture of the detailed sequence of events during individual voids' coalescence to cracking. Also, the two-step damage classification method was used to analyze the progressive damage mechanism of 3D5D braided composites under fatigue loading. Debonding dominates the fatigue damage propagation in the material within 76.9% of fatigue life and accounts for 82.5% of all fatigue damage. The voids located at the interface of yarns were inferred to be the critical voids under fatigue loading. More significantly, the deflection of the crack front of the voids was quantified via automated algorithms. It is expected that this study can provide unparalleled quantitative data for the development of fatigue life prediction models of 3D5D braided composites with voids.

Automated summary

The objective of this study is to analyze the effect of voids on damage evolution in 3D5D braided composites under fatigue loading. Micro-CT and novel image algorithms were used to capture the detailed sequence of events during void coalescence to cracking. Debonding dominates fatigue damage propagation and the voids located at the interface of yarns are found to be critical. The deflection of the crack front of the voids was quantified using automated algorithms.