Improving the D2512 Lox Compatibility of Composites by Using Thermally Conductive Graphite Fibers
Final rept. 1 Jul 2001-1 Apr 2005
AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE
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This effort demonstrated that using a thermally conductive fiber substantially enhances a composites ASTM D2512 mechanical impact liquid oxygen compatibility. It repeatedly achieved 90 of the goal of passing D2512 with a 1700 improvement over baseline. This effort also documented the types of fracture surfaces routinely found in the residuals of the materials investigated. These fracture surfaces indicate that hertzian fracture is the mechanism by which a specimen fractured and failed. The fracture surfaces routinely indicated that kinetic friction associated with signs of intense heating occurred. Kinetic frictions mechanical-to-thermal transformation mechanism provided the only phenomenological explanation for the extremely rapid and large temperature rises required for conditions recognizable as ignition to occur in the time frame of a D2512 test. The effort crystallized the sequence from fracture to heating to ignition. First, a series of hertzian fractures develop. These allow kinetic friction of the hertzian fractured material to occur. Kinetic friction transforms mechanical energy into temperature rising thermal energy. This thermal energy causes the material to degrade by radical chain scission and oxidize by radical addition peroside chemistry to a degree detectable as ignition.
- Laminates and Composite Materials