A rapid prototyping process enables the incorporation of continuous fiber reinforcement into a cast metal-matrix composite. In one older process, cast metal-matrix composites are made by introducing fibers or particles into molten or partially solidified metals, then casting the resulting slurries into molds. In an older process, masses of particles are preformed, then molten alloys are infiltrated into the masses. The alloys then freeze in the interstices, forming metal-matrix composites.
In the rapid prototyping process, fibers are inlaid into a wax model that is later shelled and cast. In a demonstration of the feasibility of the process, a fused-deposition apparatus was used to make a model tensile bar. For concept verification trials, the intervals between fibers were determined and grooves were carved into two tongue depressors at those predetermined intervals. Each tongue depressor was taped onto opposing ends of a sample wax model. A fiber was then placed into each groove of one tongue depressor and taped down. The fibers were then drawn across the build space and placed into the grooves of the tongue depressor on the other side and taped down. This resulted in a framelike structure made of the fibers strung between the two ends.
This framelike structure was removed from the wax model and another one constructed using the same method. The fused-deposition apparatus was preprogrammed to pause between successive layer-building processes to enable the innovators to construct another frame.
For these trials, emphasis was placed on the applicability of producing continuous-fiber-reinforced metal-matrix composites by rapid prototyping. Therefore, a simple alignment of fibers previously proven to strengthen the part being built was used. However, there is a need to incorporate metal-matrix composites into regular production parts, and not into tensile-test bars only.
Although these concept verification trials involved linearly aligned fibers, the innovators are currently working on conceptual designs for circularly aligned fibers.
This work was done by Floyd E. Roberts and Erica Dudley of the Marshall Space Flight Center. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com under the Manufacturing and Fabrication category, or circle no. 192 on the TSP Order card in this issue to receive a copy by mail ($5 charge).
Inquiries concerning rights for the commercial use of this invention should be addressed to
the Patent Counsel
Marshall Space Flight Center; (205) 544-0021.
Refer to MFS-31180.