Debonding Behavior Characterization of Fiber Matrix Interface using a Cruciform Model Composite with Multiple Fibers

A cruciform specimen with multiple fibers is used to evaluate the fiber/matrix interfacial tensile strength. The model composite contains thick fibers for the precise detection of the debonding initiation location. By arranging two fibers the influence of the adjoining fiber on a debonding behavior can be estimated. The fibers are aligned parallel each other and perpendicular to the loading direction. The effect of the interval between two fibers on the debonding behavior is observed. FEM analysis that has been carried out beforehand shows that the stress concentration at the inner pole of an interface becomes large as a fiber interval becomes small. However, it is experimentally observed that the debonding initiation occurs at the outer pole. Since this behavior is considered to be due to the cure shrinkage of resin, FE analysis in which thermal expansion is incorporated as chemical shrinkage was conducted. As a result of the analysis, it is explained that debonding initiates at the interface angle of 90 degrees.