Browsing by Author "Klug, Thomas"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
- ItemAlternating bending load behaviour of unidirectionally fibre-reinforced glasses(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1992) Klug, Thomas; Bornhöft, Hansjörg; Brückner, RolfAlternating bending load experiments are described and applied on SiC- and carbon-fibre-reinforced alkaline earth borosilicate glass samples. The mechanical properties (strength, bendover stress, Young's modulus) were determined by the three point bending method after 1000 strain-controlled alternations of load and compared with those of non-pretreated samples. It could be shown that all composites can be treated by an alternating bending load up to their elastic proportionahty limit (bendover stress) without failure or without any loss of their mechanical properties. Alternating bending loads above the bendover stress lead to a rapid fatigue of the SiC-fibre-reinforced glass composites while the carbon-fibre-reinforced composites show a great toleration of damage under the applied experimental conditions. In the case of the carbon-fibre-reinforced glass the homogeneity of the fibre distribution is of special importance for high bendover stresses and strengths during cyclic bending load experiments.
- ItemSiC- and carbon-fibre-reinforced glass under alternating bending stress loadings(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1992) Klug, Thomas; Brückner, RolfAlternating bending stress experiments are described which were performed with various fibre/DURAN-glass composites reinforced by Nicalon NL 202 SiC fibres and by two different types of carbon fibres, a high-tensile strength (ht) and a high-modulus (hm) fibre. Also the influence of unidirectionally homogeneous and inhomogeneous fibre distribution as well as the bidirectional 0°/90° ply distribution are studied. In contrast to previously investigated strain-controlled experiments the present stress-controlled experiments show after the pretreatment of 1000 alternating tensile-compressive stress cycles fatigue (beginning damage) already at amplitudes below the limit of pure elasticity (below bendover stress) of a simple bending-load experiment. Despite of this difference the "training effect" of the previous investigation, the increase of the bendover stress with increasing stress amphtude after 1000 alternating-load cycles, is found to be similar and can be established also for the present experiments. The carbon-fibre-reinforced composites show a better tolerance of damage due to their smaller fibre diameters than the SiC-fibre-reinforced composites.
- ItemThermal expansion behaviour of fibre-reinforced DURAN glass(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1993) Klug, Thomas; Fleischer, Veronika; Brückner, RolfThe thermal expansion coefficients of DURAN glass reinforced by SiC and various carbon fibres are determined in order to investigate the influence of the different types of fibres and the preparation parameters on the thermal expansion behaviour of the composites. The coefficient of thermal expansion decreases with increasing Young's modulus of the fibres and with increasing fibre volume content. Composites with high-modulus carbon fibres and/or with high fibre volume concentration show a transition from contraction at lower temperatures to expansion at higher temperatures. "Zero expansion composites" can be produced for certain temperature intervals by selection of the fibre types and the fibre volume concentration. The experimentally determined expansion coefficients are compared with the theoretically calculated ones by the mixing rule. The agreement is very good for the high-modulus fibres, less good for the high-strength fibres.
- ItemThermal shock behaviour of SiC-fibre-reinforced glasses(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1992) Klug, Thomas; Reichert, Jutta; Brückner, RolfThe preparation of two SiC-fibre-reinforced glasses with very different thermal expansion coefficients and glass transition temperatures is described and the influence of long-time temperature and thermal shock behaviour of these composites on the mechanical properties is investigated by means of bending test experiments before and after thermal treatments. It will be shown from experiments and calculations on stresses due to thermal expansion mismatch between fibre and glass matrix that not only best mechanical properties but also best thermal shock behaviour are connected with low tensile intrinsic stresses produced by thermal expansion mismatch during preparation. The thermal shock resistance of the best composite (SiC fibre/DURAN glass) does not show a significant decrease of flexural strength even after 60 shocks from 550 to 25 °C in water, while the bulk glass sample of the same dimension was destroyed by one thermal shock from 350 °C.