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End date: 2019 × Start date: 2019 × End date: 2019 × Start date: 2011 × DDC: 570 × Type: Article × Subject: mechanical properties × WGL Institute: INM ×

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    Timescales of self-healing in human bone tissue and polymeric ionic liquids
    (London : Institution of Civil Engineers, 2014) Akbarzadeh, Johanna; Puchegger, Stephan; Stojanovic, Anja; Kirchner, Helmut O.K.; Binder, Wolfgang H.; Bernstorff, Sigrid; Zioupos, Peter; Peterlik, Herwig
    Strain (stress-free) relaxation in mechanically prestrained bone has a time constant of 75 s. It occurs by a reorganization of the proteoglycan-glycoprotein matrix between collagen fibers, which requires ionic interactions. Dissolving and relinking the ionic bonds is thus an important tool of nature to enable plastic deformation and to develop self-healing tissues. A way to transfer this approach to technical materials is the attachment of ionic end groups to polymeric chains. In these classes of materials, the so-called polymeric ionic liquids, structural recovery of thermally disorganized material is observed. A time constant between minutes and a week could be achieved, also by ionic rearrangement. The same mechanism, rearrangement of ionic bonds, can lead to vastly different relaxation times when the ionic interaction is varied by exchange of the cationic end groups or the anions.
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    Structure-property relationships in mechanically stimulated Sorghum bicolor stalks
    (Berlin : de Gruyter, 2014) Lemloh, Marie-Louise; Pohl, Anna; Zeiger, Marco; Bauer, Petra; Weiss, Ingrid M.; Schneider, Andreas S.
    Mechanical properties of plants and underlying structure-property relationships are important for agricultural purposes as well as for biomimetic concepts. In this study, the effect of mechanical stimulation on morphology and bending properties of the stalk was investigated for Sorghum bicolor (Poaceae), a widely used drought-tolerant biomass grass. An experimental set-up allowing for defined growth and mechanical perturbation (flexing) during a defined growth period was designed. Mechanical properties of individual internodes of the stalk were determined by three-point bending tests. We found that the three investigated lines showed differences in their general bending strength in the non-stimulated condition. However, similar high range of bending strength values was measured for all plant lines after they underwent the mechanical stimulation procedure. The anatomy of internode cross-sections was examined to evaluate structure-property relationships. An increased thickness of the outer sclerenchymatous tissue was observed for internodes with higher bending strength values. Dried internodes fail under lower strains but showed higher bending strength. These findings show that mechanosensitivity in sorghum is dependent on genetic as well as environmental factors. The experimental system presented here offers new straight-forward possibilities for S. bicolor line selection for applications requiring mechanical strength of the stalk.