ESA Initiatives to Improve Mechanical Design Verification Methods for Ceramic Structures

摘要

Current and future space missions demanding ever more stringent stability and precision requirements are driving the need for (ultra) stable and lightweight structures. Materials best suited to meeting these needs in a passive structural design, centre around ceramic materials or specifically tailored CFRP composite. Ceramic materials have essential properties (very low CTE, high stiffness), but also unfavorable properties (low fracture toughness). Ceramic structures feature in a number of current and planned ESA missions. These missions benefit from the superior stiffness and thermo-elastic stability properties of ceramics, but suffer the penalties inherent to the brittle nature of these materials. Current practice in designing and sizing ceramic structures is to treat ceramic materials in a deterministic manner similar to conventional materials but with larger safety factors and conservatively derived material strength properties. This approach is convenient, but can be penalising in mass and in practice does not arrive at an equivalent structural reliability compared to metallic components. There is also no standardised approach for the design and verification of ceramic structures in Europe. To improve this situation, ESA placed two parallel study contracts with Astrium and Thales Alenia Space with the objective to define design and verification methodology for ceramic structures, with the further goal to establish a common 'handbook' for design and verification approach. This paper presents an overview of ceramic structures used in current and future ESA missions and summarises the activities to date in the frame of improving and standardising design and verification methods for ceramic structures.