2 May 2007 Characterization of AFB sapphire single crystal composites for infrared window application
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Abstract
Next generation weapons platforms may require 30" x 30" sapphire windows. Since these sizes exceed what can be manufactured directly, a concept is proposed and experimental data are furnished in this report on the viability of increasing the window dimensions by Adhesive-Free-Bonding (AFB®) of smaller starting components by their edges. The bonding scheme has been evaluated for single crystal sapphire but is expected to also work equally well for other IR window materials. The bonding mechanism is explained with Van der Waals theory of attractive forces and confirmed experimentally by applying the bending plate theory. The gap at the interface between two components is deduced from the measured roughness of the polished surfaces that are brought into optical contact and subsequently heat-treated, and is estimated to be about 2 Å rms. Stress relief at AFB® interfaces has been established. Experimental data of flexural strength determined by four-point bending at room temperature is reported. The data indicates that AFB® composite specimens and equivalently prepared blank samples fracture at statistically same loads under standardized testing conditions. Failure of composites has not been observed at the interface and only at random flaws that are a result of sample preparation.
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H.-C. Lee, H.-C. Lee, H. E. Meissner, H. E. Meissner, } "Characterization of AFB sapphire single crystal composites for infrared window application", Proc. SPIE 6545, Window and Dome Technologies and Materials X, 65450K (2 May 2007); doi: 10.1117/12.719436; https://doi.org/10.1117/12.719436
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