Time-dependent deformation of surface geometry on light weight and thermally stable CFRP mirror in humid environment

Abstract

CFRP (Carbon Fiber Reinforced Plastics) is the ideal material for space based mirror due to its low thermal expansion, and high specific modulus. To expand the use of CFRP, we investigated the long-term stability of CFRP under humid environment. CFRP mirror was made as precise as possible by using special class of material and adopting particular design techniques. Dimensional stability of CFRP mirror was evaluated by nano-scale measurement. The factors which cause out-of-plane deformation of the mirror is discussed.

CFRP composite mirrors for space telescopes and their micro-dimensional stability

“…Roughness was 30nm RMS and 20nm RMS respectively. Roughness of the coat surface could be improved by polishing or resin coating conditions [5]. 1~2nm RMS surface roughness was achieved by optical-polishing or diamond turning reported by COI [6].…”

Carbon Nanotube Layer for Reduction of Fiber Print-Through in Carbon Fiber Composites

“…A telescope is composed of several components, with the primary mirror being the most important, since its function is to collect and focus the light [1][2][3]. In a telescope, a typical mirror has a mass of approximately 30 kg, increasing for 150 kg when the support structure is added [3].…”

“…The fiber print-through effect is one of the main problems about using the CFRP in optical mirror, which contributes to the reduction of mirror smoothness and accuracy [1]. Fiber print-through occurs when the ribs or fibers overlap each other in the mirror surface, creating residual stresses during the solidification process [1,2,4].…”

“…Here, the authors concluded that both mitigate fiber print-through, but the lack of uniformity of magnetic field density and the relationship between the print-through amplitude and the thickness of the resin layer are imperceptible. Arao et al [2] applied a 2 Advances in Polymer Technology resin layer in CFRP surface and observed that, for uncoated samples, RMS (root mean square) was 120 nm, being reduced for 10-20 nm with resin coating application. Kamiya et al [10] applied the same method and obtained a reduction of RMS from 510 nm to 5.1 nm.…”

Large aperture telescope technology: a design for an active lightweight multi-segmented fold-out space mirror

“…Recent work on similar CFRP honeycomb structures [5] has demonstrated improved optical tolerances, however more research is required to bring the mirrors within optical specifications.…”