Single Fiber Interfacial Shear Strength Test of Fiber Reinforced Polymer Composites: A Review

The single fiber interfacial shear strength (IFSS) is a critical parameter for evaluating the micro‐mechanical properties of fiber reinforced polymer composites, as it directly influences their macroscopic mechanical behavior, such as their strength, toughness, and failure modes. To accurately evaluate this property, researchers have developed a series of testing techniques, such as the microdroplet debonding test, the fiber pull‐out test, and the single fiber fragmentation test (SFFT). Previous reviews on the characterization of IFSS typically focused only on the principles of different methods and subsequent data analysis. Here, their fundamental principles, core equipment and consumables, sample preparation procedures for both thermosetting and thermoplastic matrix materials, and influencing factors on the test results are systematically introduced. Meanwhile, the extension and theoretical innovation of the SFFT for applying to the short fibers are reviewed. In addition, the principles of the fiber push‐out test method and Raman‐FEA method are briefly introduced. This review aims to provide researchers in the field of fiber reinforced polymer composite materials with a comprehensive understanding of the testing methods for single fiber interfacial shear strength, and to provide a reference for selecting an appropriate method and subsequent implementation testing.