Novel, Nanotechnology Based CMC Composites for Hot Structures

Very extensive R&D efforts over the past several decades resulted in several classes of high temperature composites offering potential for future hypersonic vehicles hot structures. Of particular interest is a hybrid carbon/SiC matrix composite utilizing carbon fiber. This class of composite, which utilizes Phenolic prepreg to form the initial composite structure, lends itself to the fabrication of large very complex structures. Typically, these composites are densified via PIP processing. However, there are deficiencies in this material system. The nature of PIP processing results in an appreciable amount of open porosity, requiring a CVD SiC external coating for oxidation protection. The application of CVD SiC to large structures is quite limited due to cost factors. Also, since the composites are fabricated using 2D fabric, the transverse mechanical properties are typically low. This proposal offers a highly innovative approach to alleviate the above mentioned shortcomings. First, it utilizes nanotechnology at the composite molding stage, enabling enhanced in plane and transverse mechanical properties. Secondly, it offers a highly unique, non CVD external coating technology. It enables the fabrication of large, complex parts with greatly reduced manufacturing cost when compared with conventional CVD SiC.