Assessment of tensile damage mechanism of open‐hole GLARE laminates based on acoustic emission and digital image correlation techniques

Abstract

AbstractGLARE laminates have emerged as a favored option for the construction of fuselage and wing skins in large airliners, owing to their exceptional mechanical characteristics. Nevertheless, the incorporation of open‐hole designs poses a challenge as it disrupts the continuity of the laminates, resulting in stress concentration and subsequent damage. To investigate the impact of various layup orientations and hole sizes on the tensile properties of open‐hole GLARE laminates, this study conducted axial tensile tests. Additionally, the tensile damage process was monitored using DIC and AE techniques, enabling the identification of damage patterns and the analysis of their evolution. The results demonstrate a noteworthy decline in the ultimate strength and failure strain as the size of the opening increases. Moreover, the retention rate of failure strain displays a marked sensitivity to the layup orientation. In conjunction with observations made through DIC and SEM, the k‐means++ algorithm successfully clustered peak frequencies, thereby revealing distinct damage patterns and their corresponding frequency ranges as aluminum alloy damage [0–90 kHz], matrix cracking [104–174 kHz], fiber/matrix debonding [175–224 kHz], interlaminar delamination [234–300 kHz], and fiber fracture [304–469 kHz]. AE cumulative counts were utilized to evaluate the progression of individual damage modes. The results emphasize that matrix cracking demonstrates the most substantial cumulative counts, whereas damage to the fibers and aluminum alloy noticeably affects the load‐carrying capability of the laminate. Furthermore, the fibers/matrix debonding and interlaminar delamination, exhibit heightened susceptibility to layup orientation and hole size.Highlights The tensile performance evaluation of GLARE laminates with open‐hole varying layup orientations and hole sizes was investigated. A combination of DIC and AE techniques was used to monitor the tensile damage process. Damage pattern was identified based on the observations of DIC and SEM. An approach based on Pearson's correlation coefficient and k‐means++ clustering algorithm was used for damage pattern recognition in GLARE laminates. AE cumulative counts were employed to assess the evolution of each damage mode.