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Furth im Wald, Germany

Dittmann J.,University of Wurzburg | Eggert A.,Fraunhofer EZRT | Lambertus M.,University of Wurzburg | Dombrowski J.,TU Munich | And 2 more authors.
Journal of Colloid and Interface Science | Year: 2016

Hypothesis: Understanding the coarsening behavior of foams is of great interest for their deliberate design. In order to systematically quantify the influence of surfactants and other chemical parameters, identifying robust descriptive features of observed foam aging dynamics is essential. Existing coarsening theories for both wet and dry foams provide concise models with respective descriptive parameters. Experiment: Multiple micro computed tomography scans of moderately wet polydisperse β-Lactoglobulin foam are recorded over a period of 15min. The growth behavior of a large fraction of about 5×104 pores that constitute the imaged volume is individually observed and statistically analyzed as a function of pore radius as well as number of neighboring pores. Findings: The three-dimensional analog of von Neumann's law for dry foams by Glazier is confirmed as a suiting empirical model, whereby a critical number of 13±7 neighbors and a diffusion coefficient of (1.8±0.8)×10-11m2/s are found for an exemplary sample. The pores growth can as well be related to their radius by means of Lemlich's coarsening model for wet foams though, whereby a critical radius marking the transition between shrinkage and growths is found to be Rc=(300±85)μm. Although different, both models fit similarly well given the broad variance of the observed growth rates. © 2016 Elsevier Inc.

Tessmann M.,Friedrich - Alexander - University, Erlangen - Nuremberg | Mohr S.,Fraunhofer EZRT | Gayetskyy S.,Fraunhofer EZRT | Hassler U.,Fraunhofer EZRT | And 2 more authors.
Eurasip Journal on Advances in Signal Processing | Year: 2010

Determining fiber length distribution in fiber reinforced polymer components is a crucial step in quality assurance, since fiber length has a strong influence on overall strength, stiffness, and stability of the material. The approximate fiber length distribution is usually determined early in the development process, as conventional methods require a destruction of the sample component. In this paper, a novel, automatic, and nondestructive approach for the determination of fiber length distribution in fiber reinforced polymers is presented. For this purpose, high-resolution computed tomography is used as imaging method together with subsequent image analysis for evaluation. The image analysis consists of an iterative process where single fibers are detected automatically in each iteration step after having applied image enhancement algorithms. Subsequently, a model-based approach is used together with a priori information in order to guide a fiber tracing and segmentation process. Thereby, the length of the segmented fibers can be calculated and a length distribution can be deduced. The performance and the robustness of the segmentation method is demonstrated by applying it to artificially generated test data and selected real components. Copyright © 2010 Matthias Temann et al.

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