The present invention relates to processes for the fabrication of two- or three-dimensional fibrous monolith (FM) composites. The invention allows articles having complex geometries to be fabricated from a single continuous fibrous monolith filament while controlling several critical processing parameters.
Fibrous monoliths (xe2x80x9cFMsxe2x80x9d) are a unique class of structural ceramics that have mechanical properties similar to continuous fiber reinforced ceramic composites (CFCCs). Such properties include relatively high fracture energies, damage tolerance, and graceful failures. In contrast to CFCCs, FMs can be produced at a significantly lower cost. FMs, which are monolithic ceramics, generally are manufactured by powder processing techniques using inexpensive raw materials. As a result of the high performance characteristics of FMs and the low costs associated with manufacture of FMs, FMs are used in a wider range of applications than heretofore typical for ceramic composites.
In preparing FM composites, starting materials typically are formed into filaments having predetermined lengths. These FM green filaments can be wound around a drum or mandrel as they are prepared to provide a desired object, or prototype, upon removal form the drum or mandrel. Other methods of forming the objects include molding, cutting and machining. Thus, in the fabrication of FM composite materials and objects, the working of the individual filaments is a labor intensive and time-consuming process.
There remains a need for a less labor-intensive process for preparing prototypes from FM composites that permits the fabrication of FM structures having complex geometries. There also remains a need for a process for preparing prototypes from FM composites to increase the production rate, reproducibility and quality of FM composite parts.
The present invention overcomes the disadvantages of prior fabrication methods. In the present invention, methods are provided for forming stronger, more durable FM prototypes. More specifically, an automated process utilizing a high pressure extruder head, which may be mechanically controlled, is utilized to extrude a continuous FM filament onto a surface, which may be mechanically controlled, to form three-dimensional objects.
In one embodiment, a computer-controlled high-pressure extrusion head with a 4-axis computer numerically controlled (CNC) motorized stage provides for extrusion and deposition of FM components. The process results in the production of solid objects directly from a computer model without part-specific tooling or human intervention. The SFF process permits the manufacture of larger, more complex parts within tighter tolerances.