Solid Freeform Fabrication: A New Process for Composite Materials

摘要

Bone is a composite material with good strength, stiffness and toughness. Anequivalent synthetic material could have many applications as a replacement for metal in structures. Various approaches to organic-inorganic hybrids let us replicate the morphological characteristics of bone: very fine particles, high volume fractions, elongated particles, tough matrices and good adhesion. interesting materials can be formed, such as surfface-hardened polymer sheets. However, the materials always become brittle as they become stiff, in the same way as do normal composites. A second look at bone shows that its toughness is due to microcracking which arises from a layered structure at the l0%um level, not from the fine scale structure. The secret is in the hierarchy. We have recently been working on one of a family of solid freeform fabrication methods. These offer a route to the formation of hierarchical structures. In our system a fine jet of polymerizable slurry is deposited under computer control. The component is built up layer by layer with curing occurring as the layers form. Since, like bone, the material is formed layer by layer, these methods also allow chemical formation of materials as opposed to conventional thermal processing. Given such a versatile route for forming materials, it is possible to produce composites, hierarchical structures, functional gradients and intelligent materials by a single process.