Microbond data analysis: comparative assessment of different approaches to determine IFSS

Abstract Studies on fiber surface modifications typically utilize micromechanical characterization methods, such as microbond tests, to assess the adhesion of a resin on a fiber. The fiber surface is thought to cause the majority of the deviation seen in the data since the surface treatment methods rarely produce uniform surfaces on all treated fibers. A realistic number of droplets must be tested to achieve reliable and statistically significant data of the fiber-matrix interface. Therefore, it is crucial to understand how the interfacial shear strength (IFSS) behaves as a function of the dataset size. An extensive microbond data analysis was conducted for a dataset consisting of approximately 1600 epoxy droplets on a commercial glass fiber (based on 53 filaments). The IFSS was calculated using three approaches to evaluate how each IFSS value behaves as a function of increasing dataset size. It was evident that the droplet’s embedded area has a significant effect on the apparent IFSS, which is troublesome if the deposited resin volume and thus the droplet size distribution cannot be controlled well during sample manufacturing. According to the results, linear regression based IFSS should be preferred but apparent IFSS may be used for comparative analysis. However, the linear regression method where a single fit is made to the whole dataset requires a high number of filaments to provide reliable results.