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DDC: 530 × Subject: Deformation ×

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    Local chain deformation and overstrain in reinforced elastomers: An NMR study
    (Washington, DC : American Chemical Society, 2013) Pérez-Aparicio, R.; Schiewek, M.; Valentín, J.L.; Schneider, H.; Long, D.R.; Saphiannikova, M.; Sotta, P.; Saalwächter, K.; Ott, M.
    A molecular-level understanding of the strain response of elastomers is a key to connect microscopic dynamics to macroscopic properties. In this study we investigate the local strain response of vulcanized, natural rubber systems and the effect of nanometer-sized filler particles, which are known to lead to highly improved mechanical properties. A multiple-quantum NMR approach enables the separation of relatively low fractions of network defects and allows to quantitatively and selectively study the local deformation distribution in the strained networks matrix on the microscopic (molecular) scale. We find that the presence of nondeformable filler particles induces an enhanced local deformation of the matrix (commonly referred to as overstrain), a slightly increased local stress/strain heterogeneity, and a reduced anisotropy. Furthermore, a careful analysis of the small nonelastic defect fraction provides new evidence that previous NMR and scattering results of strained defect-rich elastomers cannot be interpreted without explicitly taking the nonelastic defect fraction into account.
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    Deformation behavior of metallic glass composites reinforced with shape memory nanowires studied via molecular dynamics simulations
    (Melville, NY : American Inst. of Physics, 2015) Şopu, D.; Stoica, M.; Eckert, J.
    Molecular dynamics simulations indicate that the deformation behavior and mechanism of Cu64Zr36 composite structures reinforced with B2 CuZr nanowires are strongly influenced by the martensitic phase transformation and distribution of these crystalline precipitates. When nanowires are distributed in the glassy matrix along the deformation direction, a two-steps stress-induced martensitic phase transformation is observed. Since the martensitic transformation is driven by the elastic energy release, the strain localization behavior in the glassy matrix is strongly affected. Therefore, the composite materials reinforced with a crystalline phase, which shows stress-induced martensitic transformation, represent a route for controlling the properties of glassy materials. The authors acknowledge the financial support of the European Research Council under the ERC Advanced Grant INTELHYB (Grant No. ERC-2013-ADG-340025) and the German Science Foundation (DFG) under the Leibniz Program (Grant No. EC 111/26-1). A DAAD-PPP travel grant is also acknowledged. Computing time was made available at ZIH TU Dresden and IFW Dresden as well as by CSC Julich. The authors acknowledge Dr. Simon Pauly and Sergio Scudino for fruitful discussions.