Fiber/matrix interfacial shear strength measured by a quasi-disk microbond specimen

A single fiber/quasi-disk microbond specimen was made for evaluating the interfacial shear strength of fiber-reinforced composites. A quasi-disk type microbond was formed with the insertion of a pin-holed Teflon film into a wetted liquid droplet epoxy resin that surrounded a single vertical carbon fiber. After finishing a curing process, the specimens were tested in comparison with conventional droplet microbond specimens. Test results for the quasi-disk type specimens showed more reliable shear strength data than those for the conventional ones. Their interfacial shear strength behaviors were in a good agreement with the hardness variation of the epoxy resin. Finite element analysis of droplet, quasi-disk and cylindrical pull-out tests showed that the stress concentration in the meniscus region for the quasi-disk type specimen was much less than that for droplet and very similar to that of the cylindrical one. This observation supported the reliability of experimental strength data measured in the quasi-disk type microbond test.