Fatigue Crack Initiation in a Carbon Black–filled Natural Rubber

Abstract

A detailed study of the initiation of fatigue cracks in carbon black–filled natural rubber is conducted. Interrupted fatigue tests are performed and fatigued samples are observed with a scanning electron microscope. This procedure first enables the quantification of the morphology, spatial distribution, and evolution of crack initiation sites for different strain levels, which gives some statistical data for each strain level. It also permits analysis of the chemical nature of inclusions inducing crack initiation thanks to energy dispersive spectrometry of X-rays. It is shown that fatigue damage initially occurs generally on carbon black agglomerates or oxides such as ZnO. However, those two types of inclusions correspond to different crack initiation mechanisms, and most of the time, only the initiations on carbon black agglomerates are followed by crack propagation that leads to failure. This difference is probably because carbon black agglomerates have a stronger cohesion than ZnO inclusions and a stronger adhesion to the matrix.

Constitutive modeling of the cyclic dissipation in thin and thick rubber specimens

“…It was demonstrated that the model compared favorably with the inelastic fatigue effects, in terms of stress‐softening and cyclic dissipation, experimentally observed in carbon‐filled SBR, by taking into consideration only the recoverable rearrangements inducing viscoelasticity in the cyclic deformation mechanisms. However, many works reported the initiation and propagation of cracks on the surface and in the core of cyclically loaded bulk specimens. The two types of dissipative network rearrangements, i.e.…”

Durability assessment via residual strength and viscoelastic observations on filled rubber compounds

“…The white star‐like dots shown in Figure represent filler aggregates. Literature survey reveals ~10 μm as a threshold diameter for fillers and their aggregates . Cracks develop easily from the aggregates larger than this level.…”

“…Literature survey reveals~10 μm as a threshold diameter for fillers and their aggregates. 1,19 Cracks develop easily from the aggregates larger than this level. Figure 2 reveals aggregates larger than~10 μm for these compounds.…”

Effects of acrylonitrile content and hydrogenation on fatigue behaviour of HNBR

“…The classification and presentation of results are similar to the one used in other studies. 20,21 All fatigue life specimens are analysed macroscopically with aid of an optical microscope. For microscopic observations, due to the time-consuming nature of microscopic analysis, only 103 specimens have been analysed.…”