No abstract

Solid Freeform Fabrication (SFF) is a new computer fabrication technique that does not require any part specific tooling. The starting material can be either solid, liquid or gaseous. The part can be made from metallic, ceramic, polymeric or a composite material. The concept is to use a solid modeling system to define the part of interest and to reduce the model to a set of toggle point data that totally define the geometry. In Selective Laser Sintering the sectioned component is then combined with a rastered laser system that impinges on the precursor powder materials in a layered reconstruction of the three dimensional CAD designed part. The part is then formed in this manner. This approach to producing the part involves a great deal of understanding of the laser materials interactions, the appropriate choice of materials specific to this processing and how the total process integrates. Application to ceramic powders will be described. An alternative approach to SFF is Selective Area Laser Deposition where the three dimensional part is made from the gas phase. The initial gas deposition studies involving deposition of carbon from hydrocarbons will be discussed. For both of the above SFF approaches the laser beam powder and gas phase interactions and the microstructure of the resulting three dimensional forms as a function of system parameters will be described.

No abstract

Further research was done on the previously reported unidirectional fiberreinforced composite tensile strength model so as to overcome the mathematical difficulties in its application. A computer program was developed to calculate the composite strength based on the composite strength model. With this computer program, the composite tensile strength can be directly calculated once certain basic fiber and matrix properties are known. Comparisons with several other composite strength models showed that this model has the best agreement with experimental data and is relatively easy to use. Applications of this model to the composite strength design were also discussed.

No abstract