Cellular structures offer high specific strength and can offer high specific stiffness, good impact absorption, and thermal and acoustic insulation. A major challenge in fabricating cellular structures is joining various components. It is well known that joints, either welded or bolted or bonded with an adhesive, serve as stress concentrators. Here, we overcome this shortcoming by the use of metal casting into 3D printed sand molds for fabricating cellular structures and sandwich panels. Furthermore, the use of 3D printing allows for the fabrication of sand molds without the need for a pattern, and thus enables the creation of cellular structures with designed mesostructure from a bevy of metal alloys. We use the finite element method to numerically analyze the energy absorption capabilities of an octet truss cellular structure created with the proposed manufacturing process and that of a solid block of the same material and area density as the cellular structure. In the numerical simulations, mechanical properties collected through experimental quasi-static compression testing are employed. It is found that indeed the cellular structure absorbs considerably more impact energy over that absorbed by a solid structure of the same weight.

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The effect of hot isostatic pressing on the bend strength of Zr02-3 mol% Y203 was critically dependent on the presintering process. Optimally sintered bodies contained no open porosity and exhibited large increases in strength following hot isostatic pressing. When open porosity of as little as 0.3% persisted after sintering, hot isostatic pressing increased the bulk density, but little or no increase in strength was realized. Two-parameter Weibull analysis of the strength data was used to quantify the strength improvement obtained following hot isostatic pressing. Typical fracture-initiating flaws were identified through optical and electron microscopy. [