Oxidation through coating cracks of SiC-protected carbon/carbon

Jacobson, Nathan; Roth, Don J.; Rauser, Richard W.; Cawley, James D.; Curry, D. M.

doi:10.1016/j.surfcoat.2008.09.013

Cited by 97 publications

(50 citation statements)

References 24 publications

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“…coating of sodium-silicate glass for further oxidation resistance [53], [55]. ________________________________________________________________________ Figure 2.9.…”

Section: Figure 27 the Specific Yield Strength Of Some High Temperamentioning

confidence: 99%

Thermal Management at Hypersonic Leading Edges

Kasen

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The intense heat flux incident upon the leading edges of hypersonic vehicles traveling through the low earth atmosphere at speeds of Mach 5 and above requires creative thermal management strategies to prevent damage to leading edge components. Conventional thermal protection systems (TPSs) include the ablative coatings of NASA's Mercury, Gemini, and Apollo vehicles and the reusable reinforced carbon-carbon (RCC) system of the Space Shuttle Orbiter. The ablative approach absorbs heat by endothermic transformation (phase and/or chemical change to the polymeric coating). The heat is dissipated from the vehicle as the single-use coating eventually vaporizes. The RCC approach manages the intense heat by operating at high temperatures and radiating heat to its surroundings. The effectiveness of both approaches is predicated on keeping the heat flux that impinges upon the susceptible aluminum airframe below a critical level.ii ________________________________________________________________________ This dissertation has explored an alternative metallic TPS concept which seeks to redistribute the heat from the leading edge, thereby eliminating local hot spots. It makes use of high thermal conductance heat pipes coupled to the leading edge so that the thermal load may be redistributed from a high heat flux location (at the stagnation point) to regions where it can be effectively radiated from the vehicle. The sealed system concept is based upon the evaporation of a fluid near the heat source that sets up a region of elevated vapor pressure inside the pipe. The latent heat is transported down the resulting pressure gradient by the vapor stream where it condenses at cooler regions, releasing the heat for removal.Replenishment of the condensed working fluid to the evaporator region is accomplished through the capillary pumping action of a porous wick which lines the interior surface of the pipe.A design methodology for a wedge-shaped heat pipe is presented which uses a coupled flow-wall temperature model to construct design maps which relate design parameters of the leading edge system (overall length, wall thickness, and alloy) to its operating conditions (isothermal temperature, maximum temperature, maximum thermal stress). Potential bounds on heat transport due to physical phenomena linked to the sound speed within a chamber (sonic limit), capillarity, and boiling nucleation are considered by extending models developed for tube designs to the wedge geometry. A new heat flux limit is proposed which, should it be exceeded, subjects the leading edge to thermally-induced plastic deformation of the TPS. iii ________________________________________________________________________To investigate the validity of the design approach and thermal spreading effectiveness of the proposed concept, a low temperature wedge-shaped leading edge was designed and constructed using stainless steel as the case material and water as the working fluid. Under localized tip heating, the maximum temperatures were significantly reduced compa...

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“…coating of sodium-silicate glass for further oxidation resistance [53], [55]. ________________________________________________________________________ Figure 2.9.…”

Section: Figure 27 the Specific Yield Strength Of Some High Temperamentioning

confidence: 99%

Thermal Management at Hypersonic Leading Edges

Kasen

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“…3 Some of these had slots machined in them; others were used in their as-fabricated form with the naturally-occurring craze cracks acting as paths for oxidation. Polishing ~300 μm of SiC off the surface revealed the cellular crack pattern as shown in figure 3(a) together with a 'skeleton' trace of the cracks in figure 3(b).…”

Section: Experimental Rcc Materialsmentioning

confidence: 99%

“…Samples were also inspected with x-ray micro-computed tomography (CT) to evaluate the true dimensions and morphology of the holes, as well as natural crack formations. 3 The controlled oxidation damage provides standards for investigating the effectiveness of various nondestructive evaluation techniques for detecting and sizing oxidation damage in this material. NASA Glenn Research Center led this investigation that had some of the top NDE specialists/facilities from NASA Glenn, NASA Langley, and NASA Marshall inspect these samples with the various NDE methods.…”

Section: Introductionmentioning

confidence: 99%

NDE for Characterizing Oxidation Damage in Reinforced Carbon‐Carbon

Roth

Rauser

Jacobson

et al. 2010

Ceramic Transactions Series

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“…These include diffusioncontrolled oxidation of the composite through coating pinholes [2] and coating cracks [3][4][5] and morphology of oxidation damage in the composite [6]. In this study, we focus only on the constituent fibers.…”

Section: Introductionmentioning

confidence: 99%

Characterization and Oxidation Behavior of Rayon-Derived Carbon Fibers

Jacobson

Hull

2010

Oxid Met

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Rayon-derived fibers are the central constituent of reinforced carbon/ carbon (RCC) composites. Optical, scanning electron, and transmission electron microscopy were used to characterize the as-fabricated fibers and the fibers after oxidation. Oxidation rates were measured with weight loss techniques in air and oxygen. The as-received fibers are *10 lm in diameter and characterized by grooves or crenulations around the edges. Below 800°C, in the reaction-controlled region, preferential attack began in the crenulations and appeared to occur down fissures in the fibers.

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Oxidation through coating cracks of SiC-protected carbon/carbon

Cited by 97 publications

References 24 publications

Thermal Management at Hypersonic Leading Edges

Thermal Management at Hypersonic Leading Edges

NDE for Characterizing Oxidation Damage in Reinforced Carbon‐Carbon

Characterization and Oxidation Behavior of Rayon-Derived Carbon Fibers

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