Study of Fiber Fracture and Interfacial Chemistry Using the Scanning Electron Microscope

Abstract

The fracture surfaces of various tire cords (bare or embedded in rubber) were examined using scanning electron microscopy, to identify fractographic features characteristic of certain load history, testing mode, or fiber microstructure. Axial splitting and fibrillation are the predominant morphological features in the fracture of aramid tire cord under either tensile or cyclic loading. Some additional topographic characteristics are also observed, for example, kink bands under MTS cyclic loading testing and a V-shaped fracture starting at the convex side of the bent fiber in the dynamic flex test. Under severe dynamic loading, conventional polyester, namely, poly (ethylene terephthalate), shows some splintering, but the splits are much shorter than those noticed in aramid fiber. Under similar testing conditions, an experimental polyester, namely, poly (ethylene-2, 6-naphthalene dicarboxylate) can develop microstructural changes leading to an unusual conchoidal fracture. The tensile fracture morphology of an experimental P-20 nylon monofil changed with changes in its tensile stress-strain behavior. Energy dispersive electron microprobe analysis of nylon monofil-rubber interface suggests that sulfur, in the form of a sulfur-zinc complex, has diffused from the rubber phase to the fiber-rubber interface, to react with the adhesive dip.