Compressive Instabilities in Metal-coated Polymer Microtrusses

With the world's industries vying to become “greener” to reduce their environmental impact, aviation has begun to look toward environmentally-friendly technologies that will not only reduce the aviation industry's impact... [ view full abstract ]

With the world's industries vying to become “greener” to reduce their environmental impact, aviation has begun to look toward environmentally-friendly technologies that will not only reduce the aviation industry's impact on the environment, but also help airline operators to save money in the process. The use of light-weight structural elements in aircraft will directly lead to a decrease in fuel consumption. A considerable interest exists in using metal-coated polymer parts as replacements for all-metal structural components. However, it is essential that an understanding of the capabilities of metal-coated polymer structures be developed first. Nanocrystalline metal-coated microtruss structures are produced by first manufacturing a polymer microtruss through 3-dimensional (3D) printing methods and subsequently coating the microtruss with nanocrystalline metal. The production methods of metal-coated microtrusses support the goals of sustainability, as 3D printing of polymer structures yields less material waste than typical metal-working techniques. Compared to traditional methods, 3D printing also allows for manufacturing of complex geometries with ease. Furthermore, the use of electrodeposition techniques for coating of the polymer structures is a well-known method with low capital costs.

Previous theoretical studies of metal-coated microtrusses have shown that their failure mechanisms are driven by compressive instabilities. As the truss elements of these structures can be modelled as metal-coated polymer cylinders, the present research seeks to explore the compressive instabilities associated with metal-coated polymer cylinders. The goal of the project is to understand the compressive failure modes associated with these metal-coated cylinders, and by extension the failure modes associated with metal-coated polymer microtrusses.

The two main failure mechanisms of interest for metal-coated polymer cylinders are local shell buckling and global buckling. Current efforts are being directed toward understanding local shell buckling. The behaviour of metal-coated polymer cylinders in axial compression can be treated as a beam-on-an-elastic-foundation problem. This approach has been used in the past for filled-shell experiments, and theoretical models utilizing this approach are in good agreement with experimental data. By choosing a suitable foundation model to represent the behaviour of the core, and combining this with well-developed theoretical models of the shell, a sound model of filled-shell local shell buckling can be derived. This model will be validated through experimental investigations and further refined as necessary. The understanding of filled-shell local shell buckling of metal-coated polymer cylinders will ultimately contribute to the failure mechanism models of metal-coated polymer microtrusses.