Sandwich-construction mirrors with foam cores and solid face and back sheets can provide high stiffness and 1c weight if the materials of construction exhibit the correct properties. A number of metallic materials with proven performance as solid mirror substrates would be suitable for solid face sheets. However, structural foams having the desired canbination of properties (low density, high shear iodulus, and high microyield/microcreep strength) have not been available. A new aluminum-silicon carbide (SXA®) canposite foam with a combination of properties which makes it very attractive for mirror cores has ten developed. The structure and properties of this foam are described in this paper. The construction and performance of SXA aluminum-matrix canposite-face sheet/SXA® canposite-foam sandwich construction mirrors are also discussed.
Alan L. Geiger,
"Metal-matrix composite foam: a new material for sandwich-construction mirrors", Proc. SPIE 1303, Advances in Optical Structure Systems, (1 October 1990); doi: 10.1117/12.21537; https://doi.org/10.1117/12.21537