Statistical analysis of acoustic emission signals and tensile deformation measurement for three dimensional carbon fiber braided composites

Accurate assessment for mechanical and damage behaviors of three dimensional carbon fiber braided composites by acoustic emission technique is difficult in practical application. In this study, a statistical analysis approach with calculated amplitude spectrum, probability distribution and entropy is proposed to process acoustic emission signals. Moreover, the tensile behaviors and damage characteristics of three dimensional four directional and five directional braided composites are investigated systematically by combining digital image correlation and acoustic emission methods. The results indicate that three dimensional five directional braided composites possess excellent load-bearing and deformation resistibility capacity, owing to more compact preform structure with additional axial yarns. The acoustic emission statistical analysis method can be used as criteria to distinguish and quantify various irreversible damage and failure mechanisms in three dimensional braided composites. Furthermore, the deformation, damage and failure criterion for two types of composites are fully described based on deformation fields and acoustic emission signals.