TY - CONF A1 - Gröschl, Christian A1 - Meyer-Scherf, Ronald A1 - Holtappels, Kai A1 - Kluge, Martin A1 - Eliezer, D. T1 - A new Technology for Hydrogen Safety: Glass Structures as a Storage System T2 - H2 - Expo CY - Hamburg, Germany DA - 2011-06-08 PY - 2011 N1 - Geburtsname von Kluge, Martin: Beckmann-Kluge, M. - Birth name of Kluge, Martin: Beckmann-Kluge, M. N1 - Geburtsname von Meyer-Scherf, Ronald: Meyer, R. - Birth name of Meyer-Scherf, Ronald: Meyer, R. AN - OPUS4-27647 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gröschl, Christian A1 - Meyer-Scherf, Ronald A1 - Holtappels, Kai T1 - Hochdruck-Wasserstoffspeicherung in Glasstrukturen T2 - 5. Symposium der Doktoranden der Abteilung 3 (PTB) CY - Braunschweig, Germany DA - 2014-01-16 PY - 2014 N1 - Geburtsname von Meyer-Scherf, Ronald: Meyer, R. - Birth name of Meyer-Scherf, Ronald: Meyer, R. AN - OPUS4-30091 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - THES A1 - Gröschl, Christian T1 - Examination of stress and strain in glass structures during pressure treatment using FEM simulation and experimental tests N2 - Glass is an amorphous material. When compared to steel, both its density and weight is three times lower. Its high theoretical strength makes it stand out as a premier material for a variety of applications. One such application is acting as a pressure resistant vessel for gas storage. Because glass has a high theoretical strength this makes it potentially suitable to withstand much higher pressures than steel or composite vessels. As a result of its brittle character, glass breaks when reaching a critical stress level. Therefore, the stress distribution during pressure load needs to be homogeneous without local stress peaks. At those peaks an initial crack will occur and the material will break. This PhD thesis is primarily concerned with the determination of the strength of several structures made of single hollow glass fibers during inner pressure treatment. Therefore, different kinds of hollow glass structures with varying parameters of shape and dimension were examined concerning their strength by determining the burst pressure. The burst pressure method was compared to the tensile test method, which poses the common test method for examining the strength of a material. The conclusion reached was that both test methods lead to comparable results and therefore, the burst pressure method poses an adequate tool for examining the strength of a hollow material against inner pressure. Another tool used in this thesis is the Finite Elements Method (FEM) simulation of internal stress and expansion of glass structures during pressure treatment. FEM was used to validate the burst pressure test results. A few selected material parameters needed to be incorporated, most notably the Young’s Modulus. Therefore, the expansion of single glass fibers was measured with light microscope during pressure load. Within the parameters of expansion, wall thickness and applied pressure, the Young’s Modulus was calculated with the Barlow’s Formula. According to the results, different two-dimensional models from single fibers to complex structures with up to 1000 single fibers were constructed and simulated with the CFD software Comsol Multiphysics. The expansion as well as the principal stress during pressure load was calculated. Different dimensions as well as different geometries of the glasses were considered to find a structure with the highest possible free volume and at the same time as less stress peaks as possible. This calculation was made in order to determine the best structure for gas storage. For this purpose the calculations were done with different dimensions of round single fibers right up to hexagonal structures consisting of more than one thousand round single fibers, which resulted in constant expansion of the structure. Furthermore, the problem of occurring interspaces between round single fibers, regarding their burst pressure-decreasing influence, was approached. Closing these interspaces with glass or other materials to avoid unsolicited pressure load led to increased strength of the structure and low storage capacities due to the increased weight and less free inner volume. The behavior of hexagonal fibers was determined as single fiber as well as in bundled condition. The walls between two hexagonal single fibers with applied inner pressure showed homogeneously distributed stress. Merely the outer walls without counter pressure showed high deformation and high structural stress. Based on that knowledge, several structures were modeled varying in different aspects. The fibers with hexagonal shape showed optimal stress distribution and high storage capacities because of high free inner volume, provided that these fibers are surrounded by additional fibers with identical inner pressure. Reducing the wall thickness for even higher free inner volume led to similar distribution but higher stress and expansion. To overcome the problem with the high stress at the outer fibers, the influence of outer fibers with different shape and dimension was simulated as well as the influence of solid glass fibers at the outer layer of the structure. The results showed that a structure with hexagonal thin-walled fibers should be surrounded by round fibers with higher wall thickness. This way the high stress peaks at the outer fibers are lowered. The examined practical strength of glass is about 100 to 1000 times lower than the theoretical strength. This is caused by defects, which may occur at the glass surface by handling or inside the material by defective production. Since the modeled results are based on the theoretical strength, the optimal wall thickness with a good compromise of strength and free inner volume needs to be found in practical tests. If further handling of the structures is necessary, an outer layer of solid fibers works as a protection layer against damages at the outer hollow glass fibers and increases the strength. Additionally, the influence of collapsing fibers inside a structure on the remaining system has been modeled as well as the influence of defects like holes or cracks at the surface or manufacturing induced defects inside the material. Any kind of defect leads to areas of high stress, whereby failure occurrence will be encouraged. In order to approve the theoretical results, the simulated structures were compared to the previously manufactured and tested ones. Due to the burst pressure test results, the tested structures showed low strength compared to the theoretical strength. This was primarily caused by the existence of defects in the material and on the surface of the glass structures. Therefore, the production process needs to be optimized in order to prevent such defects. Furthermore, an additional protection against outer influence like air humidity or the physical contact to other materials is required. KW - Glass structures KW - Hollow fibres KW - Stress and strain PY - 2016 SP - 1 EP - 252 PB - Universitätsbibliothek CY - Magdeburg AN - OPUS4-39257 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -