Shear Modulii For Cellular Foam Materials And Its Influence On The Design Of Light-Weight Mirrors

Abstract

New demands on the performance of light-weight optical systems have led to the design and development of light-weight foam core mirrors for various applications. Foam core mirrors offer the advantage of additional weight savings without sacrificing optical performance. The design of a foam core mirror is complex and the optical performance depends largely upon the various mechanical design parameters. Although the elastic modulus, E, of the core material is important, the optical performance of light-weight mirrors is highly sensitive to the core shear modulus, G. Therefore, to effectively design a light-weight foam core mirror, the value of G for the core material must be established with a high level of confidence. This paper addresses the theoretical analysis and test method utilized to accurately determine the shear modulus for cellular foam materials and illustrates the significance of G as a parameter in the design of light-weight mirrors.