Correlation of fiber orientation and fiber-matrix-interaction of injection-molded polypropylene cellulose fiber composites

Based on the varying fiber orientation in injection-molded composites, this study is focused on characterizing the fiber matrix adhesion of varying embedding angles of regenerated cellulose fibers (RCF) and glass fibers (GF) in a Polypropylene (PP) matrix with varying contents of maleic anhydride acid (MAPP) as coupling agent. The interfacial shear strength (IFSS) and critical fiber length (l(c)) were determined using the single fiber pull-out test (SFPT). The results showed that the IFSS and l(c) of fibers with an embedding angle> 0 degrees can only be calculated with a correction factor from the standard SFPT with an angle of 0 degrees. Furthermore, a comparison of the resulting angle-dependent lc with the angles and lengths of several thousand fibers in representative injection-molded specimens, characterized by X-ray microtomography, allowed a detailed calculation of the amounts of fiber pull-outs and ruptures for a very precise statement of the failure processes e.g. for fracture mechanical models.