Abstract: A method for forming a composite structure, using a mandrel that is later removed from the composite structure, involves production of a mandrel by depositing a particulate mixture, including an aggregate and a binder, into a mold and removing the mandrel from the mold. The mandrel may be treated while still in the mold by heating, curing with an agent, microwave energy, or by some combination thereof. Once finished, the mandrel can be used in manufacturing polymer and/or composite components. The mandrel can also include materials that can be easily removed from the finished composite structure by water, shakeout, chemically dissolving, or by some combination thereof. The mandrel can be a self-expanding mandrel, and can be used in a process or system for the manufacture of composite structures.

Abstract: A tool, such as a monolithic ceramic round tool or ceramic inserted round tool fabricated from materials containing silicon nitride, is used for machining composite materials, plastics, and graphite. The tool contains at least a ?-silicon nitride phase and a grain boundary phase that is composed of rare earth element oxides such as zirconia, yttria, ceria, and compounds that contain elements such as aluminum, magnesium, silicon, nitrogen and oxygen. The tool is formed by consolidating powder components at elevated temperature. The consolidated ceramic has a porosity of less than 2 vol. %. Composite materials that can be machined include glass fiber-polymer composites, whisker reinforced polymer composites, and carbon fiber containing composites.