Transparent glass fiber/glass matrix composites

The industrial production of SiC- or C-fiber reinforced glasses or glass ceramics is state of the art. Reinforcement leads to an improvement of fracture toughness, thermo-shock resistance and, especially, mechanical strength. The temperature stability is limited by matrix softening. For realizing this improvement the mechanical properties of the composite components have to be fitted each other, e.g. a definite ratio of Young’s moduli and nearly equal thermal expansion coefficients. At that a special interface design, realized by fiber coating or in situ during the manufacturing process, acts as a reaction and diffusion barrier and prevents the linkage of fiber and matrix. Presently available commercial products are dark coloured and intransparent for visible light. Additionally they are expensive apparently according to the low demand. The aim of our work is making such composites as described above transparent for visible light. Therefore the optical properties, e.g. the refractive index, of the components have to be matched to each other, additionally to the mechanical properties. We chose S-Glas- and the nanocrystalline NextelTM fiber as the reinforcement components for different glasses. First results have shown nearly 50% transmission for the new material but the absence of fiber debonding results in brittle fracture behaviour. However, the mechanical strength was increased by energy dissipation. At present further nonoxidic (BN), oxidic (SnO2, TiO2, ZrO2), and double fiber coatings will be tested to achieve the aspired properties. The results will be given in the poster.