Stratasys' Fused Deposition Modeling (FDM) is a typical Rapid Prototyping (RP) process that can fabricate prototypes out of plastic materials, and the parts made from FDM were often used as load-carrying elements. Because FDM deposits materials in about 300 μm thin filament with designated orientation, parts made from FDM show anisotropic material behaviors. This paper proposes an analytic model to predict the tensile strength of FDM parts. Applying the Classical Lamination Theory and Tsai-Wu failure criterion, which were developed for laminated composite materials, a computer code was implemented to predict the failure of the FDM parts. The tensile strengths predicted by the analytic model were compared with those of the experimental data. The data and predicted values agreed reasonably well to prove the validity of the model.

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In our research, Ti-Ni and Ti-Ni-Cu alloy powders were fabricated by mechanical alloying, and then phase transformation behaviours were investigated by means of X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis and transmission electron microscopy. The size of the Ti-Ni-Cu alloy powders decreased as Cu-content increased. The powders of as-milled Ti-Ni and Ti-Ni-Cu alloys with Cucontents less than 5at.% were amorphous, whereas those of as-milled Ti-Ni-Cu alloys with Cu-content more than 10at.% were crystalline. These characteristics indicate that Cu addition tends to suppress amorphization of Ti-Ni based alloy powders. The monoclinic B19' martensite is formed in the Ti-Ni-Cu alloy powders with Cu-content less than 10 at.%, whereas the orthorhombic B19 martensite is formed in the Yi-Ni-Cu alloy powders Cu-content more than 10 at.%. The Fe contamination is reduced by decreasing rotation speed from 350 rpm to 250 rpm.

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