Critical analysis of adhesive layer behavior in patch-repaired carbon fiber-reinforced polymer panel involving digital image correlation

Abstract

In the present work, critical strain field in thin adhesively layer of double-sided (symmetrical) patch-repaired carbon fiber-reinforced polymer composite panel under tensile load is investigated using digital image correlation technique. Longitudinal, peel, and shear-strain distribution in adhesive layer is analyzed thoroughly in repaired panel by performing global cum local strain field analysis involving digital image correlation. Effective load/shear transfer length in repair configuration is estimated based on global strain analysis, and further, it is compared with the one predicted from finite-element analysis. Localized strain analysis using magnified optics provides higher resolution, and it is found useful in revealing complex strain field in small but critical zones responsible for failure initiation. The global and local-strain analyses are found complementary to one another, and therefore both are essential to fully characterize the strain field in thin-adhesive layer. The critical failure mechanism is also investigated and correlated with the load–displacement behavior. DIC is found to be suitable and accurate for analyzing the global and local strain field over small but critical locations and helps in predicting the damage-initiation location based on strain anomalies. Finally, the experimental results are compared with the numerical predictions, and they are found to be in good correlation.