First‐Time Investigations on Cavitation in Rubber Parts Subjected to Constrained Tension Using In Situ Synchrotron X‐Ray Microtomography (SRμCT)

Abstract

Typically, rubbers and rubbery materials are characterized by their macroscopic properties, that is, by the mechanical behavior under external load. However, the macromechanics of rubbers are influenced by the microstructure of the polymer network, for example, the average crosslinking density and the presence of fillers, such as carbon black (CB) or silica. As a consequence, knowledge of the micromechanical deformation and failure behavior is essential for the right choice regarding the compound and the design of technical rubber parts. The first approaches to monitor the deformationinduced structure evolution in rubbers have been performed using advanced imaging techniques, that is, 3D transmission electron microscopy (3D-TEM). Nusser et al., [1] Das et al., [2,3] and Kadowski et al. [4] have shown that nanoscale morphological analysis of rubber composites is possible with the help of 3D-TEM. As a result, the knowledge of the evolution of the microstructure of filler-reinforced rubber materials could be improved by information that is barely accessible in 2D methods, for example, the existence of percolated networks [1] or the presence of individual thin layers of graphene nanoplatelets. [2,3] Furthermore, results of highresolution 3D-TEM experiments were used for finite element analysis (FEA) to model the nanostructure between filler aggregates, that is, the glassy bridges. [4] However, the 3D-TEM technique has some drawbacks: 1) The 3D reconstructions are

Insights into the cavitation morphology of rubber reinforced with a nano-filler

“…The cavity size in NR reinforced with CB was smaller for samples with high filler content than those with low filler content 10 . The same trend was observed in SBR reinforced with CB 31 , revealing that the number and size of cavities increased with strain, and as CB content increased, cavity size decreased while their number increased. In these studies, the terms “void” and “lower-density rubber area” were used interchangeably with “cavity.” The 4D-CT results confirmed that higher silica content led to smaller void sizes and lower-density rubber areas, as seen in Fig.…”

“…Although microscopic voids were not clearly observed in the lower-density rubber area at the effective pixel size of this study (13.2 μm), tiny satellite cavities were identified in the walls of neighboring microscopic cavities using micro-CT with a higher spatial resolution 31 . In addition, nanovoids were revealed using in situ small-angle X-ray scattering 33 and transmission electron microscopy 24 under deformation.…”

“…Comparisons of cavitation morphologies in rubber samples with varying filler amounts have been reported 10 , 31 , 32 , with a primary focus on the analysis of the size and number of cavities formed in the rubber. The cavity size in NR reinforced with CB was smaller for samples with high filler content than those with low filler content 10 .…”

Experimental study on cavitation in rubber vulcanizates subjected to constrained tensile deformation

“…Thus, the presence of a moderate amount of CB can be understood as intrinsic microstructural constraints affecting the cavitation in terms of the number and size of single cavities. Due to the outstanding high phase-contrast, experimental data obtained by synchrotron-µCT measurements have confirmed, that for SBR vulcanizates containing moderate amounts of CB, major cavities are surrounded by tiny satellite cavities not detectable by conventional µCT [7]. In the case of CB contents ≤ 20 parts per hundred rubber (phr), the cavity formation and growth is suppressed due to the presence of CB agglomerates.…”

Machine-learning-revealed reaction statistics via 3D spectroimaging for copper sulfidation of adhesive layers in rubber/brass composite

“…Hard X-ray/neutron scattering techniques [31,32] and CT [33][34][35][36] of rubber-filler composites were used in the pioneering analysis of rubber materials, but the spectroimaging of the sulfidation of brass Cu species in rubber composites has not yet been reported. Hard X-ray spectroimaging, which is the most powerful tool for visualizing chemical information in bulk materials non-destructively [37][38][39][40], and Hard X-ray absorption fine structure spectroscopy with computed tomography (XAFS-CT) is performed by CT with different X-ray energies and provides 3D images of spectroscopic information, such as amount, valence state, and local coordination of each chemical species in composite materials [41][42][43][44].…”