The combination of the structure of origami folding geometries and the strength of carbides has the potential to create strong yet flexible low density parts. For the structure aspect, the Miura-ori origami geometry is able to fold compactly or unfold into a panel, allowing it to deform as loads are applied. Tungsten carbide is chosen as the potential carbide due to its extreme hardness and relatively high Young’s modulus of 530-700 GPa. Previous work by our group showed how the heat treatment of a Miura-ori geometry, made with cellulosic paper infiltrated with a tungsten precursor, yielded a rigid Miura-ori tungsten carbide structure. Here, we focus on studying the effect of crease geometries and materials as it relates to the specific strength of the Miura-ori carbide structure.

The crease geometry is a function of the cutter plotter’s inputs, specifically including creasing force, crease width, and the number of passes over each crease. These variables are varied using the Taguchi design of experiment in order to determine the optimal crease geometry that will yield the highest Young’s modulus. The main challenge has been to crease the paper without it ripping, as this sometimes occurs when the force is high and the line thickness is small. After creasing, the structures are folded and then carbonized (Fig. 1). The carbonized Miura-ori structure is then load tested to determine the Young’s modulus and, knowing the dimensions of the part, the specific strength.

To determine how the tungsten carbide affects the strength of the material, an inkjet printer deposits an ammonium metatungstate [AMT] solution onto the paper after it is creased. When the structure is carbonized, the AMT decomposes and forms tungsten carbide in the presence of the carbon in the paper. This process yields a Miura-ori structure that is at least partially tungsten carbide. Different concentrations of AMT solution should yield greater percent tungsten carbide in the carbonized part, which is something that will be explored in the future.

Ongoing work is on characterizing the effect of processing on the mechanical properties of the carbon structures. To this end, the carbonized parts are load tested to determine their Young’s modulus and the specific strength. These explorations into the part’s physical geometry and composition will allow for optimization of the structure’s strength through physical and chemical optimization.

References

Schenk, M., & Guest, S. (2013). Geometry of Miura-folded metamaterials. Proceedings of the National Academy of Sciences of the United States of America, 110(9), 3276-3281.