Toughness in hard biological tissues is associated with fibrous or lamellar structures that deflect or stop growing cracks. In some cases, such as nacreous shell, protein interlayers absorb much of the crack energy. In other tissues, such as tooth enamel, the toughness derives from the mineral microstructure, and the small amount of residual protein apparently has little effect. There have been a number of efforts to make tough synthetic materials using layered structures. In this work, freeform fabrication has been used to make layered structures with a view to introducing similar toughness into brittle materials. Results are presented for epoxy-glass composites with glass fabric interlayers, porous alumina back-filled with aluminium metal, and layered glass-ceramic/silver materials.

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Direct fabrication of alumina parts by robocasting was completed. This method is based on three-dimensional deposition of binderless aqueous alumina slurries. Parts were made with different deposition paths and mechanical testing performed to determine the effects of bead alignment. Properties were also compared to alumina processed more traditionally.

Freefonn fabrication is a family oftechniques for preparing solid objects from a three-dimensional computer-based design. The best known method is stereolithography. To date, freeform fabrication has been mainly applied to making prototypes and molds. Similar techniques can be applied to make functional parts of a range materials, including metals and ceramics as well as polymers. In collaboration with Advanced Ceramics Research Corp. of Tucson, Arizona, we have been developing a reactive extrusion method where a part is built up by extrusion of a material stream through a fine needle. A curing reaction at the deposition site allows solid components to be formed. This approach can be readily modified to deposit several materials in the same part and hence to fabricate intelligent materials containing embedded sensors and actuators. This paper describes the application of this method to an epoxy part containing an optical fiber sensor and the response ofembedded polyvinylidenefluoride piezoelectric films. O-8194-2165-O/96/$6.OO Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/15/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx

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