Influence of cyclic loads on the fiber-matrix-interaction of cellulose and glass fibers in polypropylene

Abstract

The present study is focused on the characterization of cyclic loads on the fiber matrix adhesion of regenerated cellulose fibers (RCF) and glass fibers (GF) in a PP matrix with varying contents of maleic anhydride-grafted polypropylene (MAPP). Glass fibers were used for reference purposes. By means of the cyclic loaded single fiber pull-out test (SFPT) the interfacial shear strength (IFFS) and the critical fiber length (lc) are determined as a function of the applied loads, the number of cycles and the MAPP content. The results of the material-specific reduction of the IFSS were extrapolated to approximately predict the fatigue behavior of the composites.The investigations show the influence of cyclic loads in the single fiber pull-out test on the fiber–matrix adhesion for the first time. On the one hand, the results show that cyclic loading of the embedded single fibers leads to a significant reduction of fiber–matrix adhesion. On the other hand, it becomes clear that the number of cycles has the greatest effect on IFSS and thus on fatigue, while the various investigated setups (test speeds and forces) show the least effect.The transfer of the resulting findings to the integral fatigue properties of composites can contribute to a much more precise property and failure prediction in the future.