Torsional damage analysis for pre-delaminated carbon/glass fiber-reinforced hybrid laminates based on acoustic emission

A torsional experiment was carried out to seek understanding of how pre-delamination influences dam-age behavior of carbon/glass fiber-reinforced hybrid composite specimens with different off-axis angles. The results revealed that an off-axis angle can improve the toughness of a composite specimen during the torsion process, and that it also has a certain protective effect on pre-delamination damage under tor-sional conditions. The delamination location has little influence on the failure torque for an off-axial structure, while for the specimen without the off-axis angle, the more inner the location of delamination the greater the reduction in failure torque. Micro-CT and scanning electron microscope (SEM) examina-tion were used for damage analysis after failure. Acoustic Emission (AE) was also applied to monitor the torsion process, and cluster analysis applied to AE signals found that they can be divided into three cat-egories with different peak frequency ranges, corresponding to three damage modes. Comparing the number of AE signals in each cluster, it found that pre-delamination specimens are more prone to delam-ination damage during the torsion process. AE data analysis results are consistent with the findings obtained using Micro-CT and SEM. The insight gained in this study can be referred for composites design and Structural Health Monitoring (SHM) for composites during their service as components.(c) 2022 Elsevier Ltd. All rights reserved.