Papers by Author: Johann Brandstetter

Abstract: Unidirectionally reinforced ceramic matrix composites (CMC) with matrix derived by pyrolysis of polymethylsiloxane or polymethylphenylsiloxane resins and reinforced with Nicalon or Nextel fibres were investigated. In order to assess and mutually compare their mechanical properties and stability when exposed to hot air up to 1200°C their elasticity moduli were measured prior to and after this exposure. The oxidation - induced damage of the material was monitored also in terms of microstructural features. Moreover, an attempt was undertaken to assess the bonding level by monitoring the push - through of macroscopic bundles of fibres using a flat indentor.

Abstract: Creep tests have been performed for carbon fibre bundles (Toray, HTA5131) in a temperature range from 1500 °C to 1800 °C and at various stress levels in a tensile testing machine in vacuum (pressure was kept below 10-3 mbar). Creep parameters have been obtained from the diagrams elongation versus time. X-rays (SAXS and WAXD) have been used for accompanying structural investigations. An increase in the alignment of the graphene sheets with respect to the fibre (and thus the loading) axis was observed with increasing test temperature. For fibres stabilised by heat treatment (2 hours, 2100 °C, without load) no creep and no structural change could be observed.