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| Home > Publications database > Experimental study on cavitation in rubber vulcanizates subjected to constrained tensile deformation |
| Conference Presentation | PUBDB-2021-05575 |
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2021
Abstract: The aim of this study was to investigate experimentally cavitation in rubber vulcanizates subjected to constrained tensile deformation. In fact, the formation and growth of cavities are induced by multiaxial stress situations. In practice, such strain constraints may occur at loaded tire treads or in bearings and bumpers.Dedicated experimental techniques were applied to investigate the mechanical properties and cavitation behavior of unfilled and carbon black (CB) reinforced styrene-butadiene-rubber (SBR) vulcanizates. By in situ dilatometry, the cavitation process was characterized indirectly by an increase of the pancake specimen´s volume due to the formation and growth of cavities. Additionally, the evolution of the cavity population was investigated by high-resolution X-ray microtomography of different beam sources, i.e. tube-based (µCT) and synchrotron radiation-based (SRµCT). The data obtained by µCT measurements show that the cavitation onset is an unstable fracture process that changes into a stable growth of cavities to release the induced stress concentrations. The results of SRµCT experiments have shown that tiny satellite cavities may appear in the walls between neighboring microscopic cavities in the case of CB reinforced SBR vulcanizates. Thus, the reinforcing fillers contribute to microstructural network constraints in addition to geometrical constraints, i.e. the shape factor of pancake specimens. The early stage of cavitation was analyzed by in situ small-angle-X-ray scattering (SAXS) experiments performed at the crack tip zone of stretched planar specimens. The results suggest a high dependency of the resistance against cavitation on the initial properties of the rubber network, e.g. entanglements or crosslinking distribution.In the literature, cavitation is often attributed to interfacial failure between the soft rubber matrix and rigid filler particles. However, the results of this study show that cavitation can even be detected in rubber vulcanizates free of fillers, such as carbon black, and free of zinc oxide, which is usually added to activate the sulfur vulcanization. This reveals that the cavitation phenomenon is not exclusively triggered by the rubber-filler-interactions. The experimentally obtained results of the present study contribute to a better understanding of the macroscopic stress-strain relation as a consequence of rubber network changes under highly constrained tensile loading. Next experiments will focus on a precise description of the origin of cavities considering the degree of rubber network heterogeneity and the microstructural changes before micro-cavities appear. In the future, experimental results will be used to enhance constitutive theories and computational analysis.
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