Effect of interfacial interaction between glass-fiber and matrix nylon-6 on nonlinear dynamic viscoelasticity and fatigue behavior for glass-fiber reinforced nylon-6

Effect of (glass-fiber/matrix nylon-6) interfacial interactions on fatigue behaviors of glass-fiber reinforced nylon-6 (GF/Ny6) under a strain controlled condition was investigated on the basis of in situ nonlinear dynamic viscoelasticity. Ny6s mixed with surface-modified and -unmodified short glass-fibers (SMSGF and SUSGF) were used as specimens. An extent of nonlinearity of dynamic viscoelasticity was expressed by nonlinear viscoelastic parameter, NVP, which was calculated from coefficients of the Fourier expanded series of the response signal during a fatigue cycle. The nonlinear dynamic viscoelasticity for both (GF/Ny6)s became remarkable with the progress of fatigue damage. The magnitude of NVP for the (SUSGF/Ny6) was always greater than that for the (SMSGF/Ny6) at a given fatigue time. Since the interface between SUSGF and Ny6 was peeled off during the fatigue test due to the weak interaction, the fatigue damage easily occurred for the (SUSGF/Ny6). Such leads to the non-uniform propagation of the imposed strain through the (SUSGF/Ny6), resulting in an increase of NVP. In the case of the (SMSGF/Ny6), the fatigue damage slowly progressed due to the strong interfacial interaction. Consequently, the nonlinearity of the dynamic viscoelasticity for the (SMSGF/Ny6) was depressed in comparison with the (SUSGF/Ny6).