This paper reviews the mechanical properties of interface adhesion between the fiber and matrix mainly by interpreting the authors' past articles. First, the methods for evaluating interface mechanical properties are described considering micromechanical testing using single-fiber composite specimens. In particular, the test-type dependence of the obtained interfacial strength is discussed, and this paper suggests that the cruciform specimen technique is an appropriate testing method. Then, this paper presents another way to obtain interface properties that is extracted from a bulk composite test. Moreover, the time and temperature dependence of the interface strength and the interface failure envelope under a combined stress state are described, respectively. Interface toughness is also discussed at the end of this paper, and it is implied that the value might be much lower than those presented in many conventional articles.
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