Characterization of The Damage Mechanism of Glass/Epoxy Composite Tubes Under Quasi-Static Axial Loading Using Acoustic Emission Monitoring

To improve the mechanical response of filament-wound composite structures, it is necessary to identify the damage mechanisms and assess the effect each mechanism has on the energy absorption capacity. To investigate this, crashworthiness characteristics of glass fiber composite tubes were experimentally studied. Due to the limitations of eye inspection and scanning electron microscopy methods, it seemed necessary to use a precise technique to gain more detailed insight into the damage mechanisms. For this purpose, the acoustic emission technique was adopted. From the macroscale view, experimental results revealed that the failure mechanisms of tubes are generated by longitudinal cracks along the winding direction due to the plastic deformation in the buckling region. On the micro-scale, the acoustic emission-based procedure based on wavelet packet transform (WPT) was adopted, where the released energy affiliated to each damage mechanism was quantified and three damage mechanisms, including matrix cracking, debonding, and fiber breakage were identified. Among them, matrix cracking was determined as the main contributor to the damage in the structure, while fiber breakage and debonding were the next main damages. Comparing the results obtained from micro and macro scales of the composite tube, the local buckling failure mode was attributed to the low content of debonding in the structure. Further, a finite element analysis (FEA) was carried out to predict the failure behavior. Key results revealed that the FEA can effectively predict the linear behavior and maximum load value of the specimen. However, some differences were found between the predicted force-displacement curves and experimental tests after the force drop.