27 June 1997 Sapphire window statistical thermal fracture characterization using a CO2 laser
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The carbon-dioxide laser provides an effective, inexpensive method for simulating aerodynamic heating in sapphire seeker windows for thermostructural testing. It has been shown, for flat, side-mounted windows, that the window edges are design controlling for two reasons. Peak stresses occur in the window edge from aerodynamic heating, and the edge strength is degraded from subsurface machining damage during window fabrication. Window edge flight stresses can be approximately replicated in small laser-heated sapphire coupons that are geometrically similar to the seeker window edge. A 3-kW carbon-dioxide laser at The Aerospace Corporation Mechanics and Materials Technology Center has sufficient power to produce flight-like thermal stresses that occur in theater missile defense (TMD) interceptor seeker windows, with ample power to produce thermal stress fracture for statistical strength margin determination. The laser approach offers several advantages over alternative methods for thermostructural testing. These include its low test cost per sample, which permits many samples to be thermally fractured to obtain statistical strength data; its repeatable, well- defined thermal loading conditions; and the absence of contamination of the window surface.
© (1997) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Daniel H. Platus, Daniel H. Platus, Oscar Esquivel, Oscar Esquivel, James D. Barrie, James D. Barrie, Paul D. Chaffee, Paul D. Chaffee, } "Sapphire window statistical thermal fracture characterization using a CO2 laser", Proc. SPIE 3060, Window and Dome Technologies and Materials V, (27 June 1997); doi: 10.1117/12.277048; https://doi.org/10.1117/12.277048

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