Piezoresistivity was found in silicon oxycarbide (SiOC) ceramics synthesized using a polymer‐to‐ceramic transformation process. A commercial polysiloxane, namely poly(methylsilsesquioxane), was used as the starting material. The SiOC ceramic synthesized at 1400°C exhibits high piezoresistivity, leading to strain sensitivities (k factors) of ∼145, while lower pyrolysis temperatures (1000°–1300°C) do not show a piezoresistive effect. Structural characterization by X‐ray diffraction in combination with micro‐Raman spectroscopy revealed that with increasing pyrolysis temperature, the content of free carbon in the X‐ray amorphous SiOC matrix increases without changes in the overall composition. Percolation effects related to the carbon‐based phase segregated from the SiOC matrix are responsible for the piezoresistivity analyzed in the SiOC ceramic.

No abstract

Market research predicts, for the aircraft industry, a large growth in the number of passengers as well as the airfreight rate with the result of this leading to increased competition for the European aircraft industry, the efficiency of new aircraft has to be improved drastically. One approach, among others, is the aerodynamic optimization of the wing. The fixed wing is designed optimally only for one flight condition. This flight condition is described by the parameters altitude, mach number and aircraft weight, all of which permanently vary during the mission of the aircraft. Therefore, the aircraft is just periodically near to the chosen design point. To compensate for this major disadvantage, an 'adaptive wing' for optimal adaptation and variation of the profile geometry to the actual flight conditions will be developed. Daimler-Benz Aerospace Airbus, Daimler-Benz Research and the German Aerospace Center (DLR) are working as project partners on concepts for a variable camber and a local spoiler bump. In this paper a structural concept developed by the DLR for the adaptive spoiler will be presented. The concept is designed under the aspect of adaptive structural systems and requires a high integration of actuators, sensor and controllers in the structure. Special aspects of the design will be discussed and the first results, analytical, numerical as well as experimental, will be presented. Part of the concept design is also the development of new actuators optimized for the specific problem. A new actuator concept for the adaptive spoiler based on a cylindrical tube and activated either by pressure or multifunctional materials (e.g. shape memory alloys) will additionally be shown.

Transmission electron microscopy was performed on a carbon‐containing SiOC material derived from a polymer precursor pyrolyzed at 1100°C and subsequently annealed at 1400°C. The TEM study focused on the correlation between micro/nanostructure evolution and the piezoresistivity monitored on the annealed sample. Upon pyrolysis, the material was completely amorphous with no local crystallization of the thermodynamically stable phases. Upon annealing, however, the formation of turbostratic carbon and SiC was observed. Unexpectedly, crystallization only occurred within intrinsic pores while the bulk of the sample remained amorphous. As the nanopores formed a percolation network throughout the entire material, the piezoresistive effect is predominantly a consequence of turbostratic carbon formation inside the residual porosity.