Reinforcing effect of aramid fibers on fatigue behavior of SBR/aramid fiber composites

This paper investigates the correlation between fatigue performance and static tensile behavior of fiber reinforced rubber materials and presents change of fiber reinforced effect during fatigue process. A rough aramid fiber (AF) surface, which is helpful for combining AF and rubber matrix, was achieved by etching AF in NaOH/CH3CH2OH solution via the hydrolysis of amide bonds on the fiber. Then, the treated fiber was coated with an epoxy-functionalized silane (gamma-propyltrimethoxysilane, KH560) and was used to prepare AF/carbon black/styrene-butadiene rubber (AF/CB/SBR) composites. The results showed that the interfacial adhesion between the complex-modified AF and the rubber matrix was further enhanced and the mechanical properties of the composite were further improved compared with those of the composite which was prepared by unhydrolyzed AF coated with KH560. The hysteresis reinforcing effect of the fiber was found after 30,000 cycles of strain-controlled fatigue, and the reinforcing effect of AF was reduced with increasing average fatigue strain. Moreover, the relative debonding energy (RDE) was calculated to evaluate the reinforcing effect of the fiber, and the RDE value sharply decreased after 30,000 cycles of strain-controlled fatigue. When the AF was treated with the NaOH/CH3CH2OH solution and then coated with KH560, the rubber composite had a high RDE value, and the fatigue life of the composite under the stress-control condition was increased approximately 4 times. The results from the characterization of the fracture appearance after 30,000 cycles of fatigue showed that the composite with the complex-modified AF could maintain better interface bonding during the fatigue process.