Lightweighting strategies for main support structures of ELT instrumentation

Abstract

This paper outlines an overview of the mechanical design of the support structure and optical bench, for ELT (Extremely Large Telescope) class of instrument utilizing standard materials. It also provides a presentation of a possible strategy to lighten this mechanical design. The mass requirements for the new class of astronomical instruments, for the Extremely Large Telescope, put tight constraints for the mechanical design of said instruments. While aluminum or steel are still the main materials that are usually employed for main support structures, carbon fiber reinforced polymer (CFRP) offers a wide range of promising possibilities. The interesting properties of carbon fibers make composite materials reinforced with carbon fibers ideal for numerous applications with high mechanical performance and low weight requirements. Carbon fibers have high strength and low weight (high strength-to-weight ratio). Furthermore, carbon fibers have a high modulus of elasticity and low thermal expansion, they are corrosion resistant and their density is lower than that of aluminum: thus, they are ideal for "light applications". In this paper two possible mechanical designs for a "large optical bench", based on different materials, are presented and compared: structural steel and carbon fiber reinforced polymer (CFRP). The models are validated through FEM Analysis approach, utilizing CAD and CAE software.