Abstract
In the field of engineering, the annual economic loss caused by material fatigue failure reaches 4% of the total economic output. The deep understanding of rubber fatigue failure can help develop and prepare rubber composites with high durability. The crack precursor sizes within the rubber composites are vital for the material mechanical and fatigue properties. In this study, we adopted three different characterization methods to analyze crack precursor sizes and their distribution. First, based on the theoretical formula of fracture mechanics, the size of the crack precursor was deduced from 180 μm to 500 μm by the uniaxial tensile experiment combined with tear test (nicked angle tear, planar tear and trouser tear). Second, by combining the uniaxial fatigue test of dumbbell specimen with the fatigue crack growth rate test, the average size of the crack precursor was calculated as 3.3 μm based on the Thomas fatigue crack growth model. Third, the average size of the crack precursor was 3.6 μm obtained by scanning electron microscope. Through theoretical calculations and experimental tests, the size and distribution of the crack precursors of rubber composites were systematically presented. This work can provide theoretical guidance for the improvement of fatigue performance of rubber composites.
Highlights
Rubber composites are extensively used in the manufacture of vibration isolators, elastic bearings, tires, seals, gaskets, and other rubber products due to its good elastic, mechanical, and dynamic properties [1,2]
The third method, through observing the low-temperature brittle fracture morphology of the rubber composites by scanning electron microscopy (SEM), we found that the crack precursor sizes were normally distributed
When the sample breaks: where T was the tear energy, Tb was the tear energy at break, Wb was the strain energy density, c0 was the crack precursor size, εb was the elongation at break, and σb was the tensile strength
Summary
Rubber composites are extensively used in the manufacture of vibration isolators, elastic bearings, tires, seals, gaskets, and other rubber products due to its good elastic, mechanical, and dynamic properties [1,2]. The fatigue failure of rubber composites is divided into two stages: Crack nucleation stage, the crack precursors inside the rubber composites gradually grow into small cracks under the dynamic stress. These defects usually became the initiation points of crack nucleation These original defects were crack precursors, whose sizes (c0 ) were usually ranged from 0.01 mm to 0.1 mm [22]. After many cycles, the crack precursors inside the rubber will gradually grow to visible small cracks, which would eventually lead to the failure of the rubber composites and bring unpredictable dangers. Based on the fatigue crack propagation theory, if we obtained the crack precursor size, the fatigue life of the rubber composite is available. The third method, through observing the low-temperature brittle fracture morphology of the rubber composites by scanning electron microscopy (SEM), we found that the crack precursor sizes were normally distributed
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