The Maximum-Strain and Strain-Interval Dependences of Microstructural Evolution Underneath the Mullins Effect

In situ small-angle neutron scattering (SANS) and constitutive model were combined to investigate silica filled deuterated silicone rubber (SFdSR) under strain rise path at strain rate of 0.001 s(-1), with strain intervals from 0.1 to 1. It was found that, (i) The non-linear behaviors are sensitive to strain interval, cycle - number, and maximum strain, etc. (ii) SANS suggests that the cyclic orientation-relaxation of bound rubber can cause accumulative fatigue. (iii) The orientation of bound rubber t(H)/t(V) - 1 decreases from 9.9 to 3.6 with increasing the strain intervals from 0.1 to 1 for the same macroscopic maximum strain 3.0. Interestingly, the mechanical response softening (E-s) and recovery hysteresis (E-rh), the evolution of bound rubber, and the constitutive analysis consistently suggests a strain threshold of 1.5. Accordingly, the roles of matrix, interface, and filler networks as well as their interactions on the origin of the Mullins effect were discussed.