High Porosity Ceramic Matrix Composite for Cooling and Drag Reduction

Historically, the porosity associated with ceramic matrix composite structures has been viewed as a detriment for many missile applications. The standard practice is to perform several treatment/retreatment processes to reduce the porosity to an acceptable level while increasing the strength of the structure. The processing methods inherent to the production of many composite materials may provide an underexplored benefit with respect to vehicle drag reduction and engine cooling for hypersonic vehicles. Several research studies have been performed using plates with slots and holes. Depending on the mass flux rate of the cooling gas, heat transfer results incorporating staggered arrays of holes have been shown to become potentially worse than those measured without cooling. Thus blowing rate, hole-patterns, and testing conditions all play a part in determining the effectiveness of this thermal management technique. One of the benefits to be quantified is the achieved uniformity of the composite matrix ceramic porosity. The intent is to demonstrate that the closely spaced openings, associated with the composite structure, does not suffer from the same drawbacks experimentally observed with distributed orifices and slotted injection techniques. Or another way to quantify it would be a very dense hole pattern per unit area that releases very small amounts of gas (zero momentum) minimizing the strength or formation of the vortex pairs that typically degrades intended performance.