Near-surface delamination induced local bending failure of laminated composites monitored by acoustic emission and micro-CT

Aiming to investigate the effects of the near-surface delamination on buckling response behavior of carbon fiber reinforced laminated composites under different bending modes, acoustic emission (AE) data analysis and X-ray micro-computed tomography (micro-CT) imaging method were promoted to characterize the mechanical properties, acoustic responses and damage visualization. Due to the existence of the artificial embedded delamination, when subjected to local compression induced by bending loads, the laminated composites showed a strong tendency to buckling behavior. The mechanical properties indicated that under different bending modes, the size of delamination had little influence on the relative change ratio of ultimate bearing capacity, but the thickness of specimen had a significant influence on the relative change ratio of ultimate load. AE monitoring results showing the characteristics of energy release for composites were related to the mutation rate of load curve. Moreover, cluster results indicate that matrix failure, interfacial failure and fiber failure are the main damage mechanisms. Micro-CT results illustrated that as the thickness of composites increases, there is a reduction in crack density. AE monitoring can reflect the initiation and evolution process of damage, and damage mechanism identification can be realized by clustering analysis. Besides, the internal damage morphologies acquired by micro-CT can directly verify the damage mechanisms. The cross-validation of AE and micro-CT can provide a basis for structural health monitoring of composites.

Automated summary

The study investigated the effects of near-surface delamination on the buckling response behavior of carbon fiber reinforced laminated composites under different bending modes. The results showed that the size of delamination had little influence on the ultimate bearing capacity, but the thickness of the specimen had a significant impact on the ultimate load. Acoustic emission monitoring and micro-CT imaging can effectively reflect the damage states and mechanisms of the composites.