Tensile and cyclic loading of fiber bundles

This paper investigated the characteristics of fiber bundles which are used for fibrous composite materials. Unembedded or dry fiber bundles were tested under monotonically increasing tensile loading. A statistical model was developed based on the slack fibers to explain the test results of the unembedded fiber bundles. Then, the behavior of the unembedded fiber bundles was compared to the fiber bundles embedded in composite materials, i.e., fiber bundles present in a matrix material. Next, unembedded fibers under tensile cyclic loadings with the displacement control mode were examined. The cyclic test results were also predicted using the statistical slack model. Finally, the residual strength and stiffness of fiber bundles were determined after undergoing different numbers of cyclic loads. Tensile tests were conducted for the same fiber bundles until failure after they were subjected to the specified cyclic loading. These tests provided data for the reduction in strength and stiffness of the fiber bundles resulting from the cyclic loading. These results would then be used in generating a cyclic fatigue failure model based on the multiscale approach that uses the cyclic test data of fibers and matrix materials instead of those of composite specimens.