Analyses of the micromechanics of stress transfer in single- and multi-fiber pull-out tests

Analyses have been carried out on the micromechanics of elastic stress transfer taking place across the fiber/matrix interface in both single- and multi-fiber pull-out tests. A two-cylinder model for the single-fiber pull-out test and a three-cylinder model for the multi-fiber pull-out test were employed in order to study the fiber pull-out problems. The difference in the stress transfer between the two models is clearly shown. Moreover, since real multi-fiber composites are inhomogeneous, the local fiber volume fraction would undoubtedly influence the stress transfer between the pulled-out fiber and the neighbouring matrix. The effect of the local fiber volume fraction on the stress transfer is discussed. When the fibers in the composite medium cylinder of the three-cylinder model are short, a fiber length factor for the composite modulus is introduced and its effect on the stress transfer is discussed. Furthermore, special attention is given to how the neighboring and remote fibers affect stress transfer. The results show that the neighboring fibers play a major role in determining the stress transfer while the influence of the remote fibers on the stress transfer is negligible. In addition, the present model for the single-fiber pull-out test is compared with other existing theories.