Fiber-matrix interactions in aramid-short-fiber-reinforced thermoplastic polyurethane composites

The mechanical and dynamic mechanical properties of thermoplastic polyurethane (TPU) elastomers reinforced with two types of aramid short fibers, m-aramid (Teijin-Conex) and copoly(p-aramid) (Technora), were investigated in this study with respect to the fiber loading. In general, both types of composites exhibited very similar stress-strain behaviors, except that Technora-TPU was stronger than Conex-TPU. This was primarily due to the intrinsic strength of the reinforcing fibers. Both types of fibers reinforced TPU effectively without any surface treatment. This could be attributed to good fiber-matrix interactions, which were revealed by the broadening of the tan δ peak in dynamic mechanical analysis. Furthermore, the morphologies of cryogenically fractured surfaces of the composites and extracted fibers, investigated with scanning electron microscopy, revealed possible polar-polar interactions between the aramid fibers and TPU matrices.