Evaluation of Fiber/Matrix Interfacial Shearing Properties by Means of Microbond Test and Finite Element Analysis

Fiber reinforced plastics are essentially heterogeneous materials where plastic matrix is reinforced by fibers. Therefore, it is important to know the properties of fiber/matrix interaction in addition to the properties of fiber and matrix themselves. To measure the fiber/matrix adhesive strength, various kinds of tests such as fiber pull-out, fragmentation, microbond, etc. have so far been tried. According to our previous study, the interfacial shearing strength by means of the microbond test was a little smaller than that of the fragmentation test, which coincided with the other researchers' result. In the present study, we tried a microbond test at four kinds of condition to establish reliable microbond test method. They are the combination of sharp or blunt microvise and two widths of microvises. We made clear that the interfacial shearing strength was different for the shape and the width of the microvise and the best method of the microbond test was to use a blunt microvise and to keep a broad width of microvise. We also made clear that the microbond test should be conducted using large microdrops to get real shearing strength. We also carried out a finite element analysis to understand the stress distribution at the fiber/matrix interface and the numerical results qualitatively coincided with the experimental result.