Using an additive manufacturing technique, scientists have developed an ultralight yet super-strong class of materials that maintain incredible stiffness even at ultralow density. The researchers predict that these materials, which are as light as aerogel yet 10,000 times more stiff, could one day prove incredibly useful in the aerospace and automotive industries. The study has been published in Science.
The new class of materials, known as microarchitected metamaterials, is the result of a collaborative effort between researchers based at Lawrence Livermore National Laboratory (LLNL) and Massachusetts Institute of Technology (MIT). These materials possess properties that are not found in nature and far outshine previous published attempts to produce similar materials.
The problem with conventional materials is that their mechanical properties deteriorate with reduced density because the structural components bow under applied load. The new materials, however, maintain almost constant stiffness per unit mass density, even at incredibly low density. The secret to this incredible strength comes from the micro-architecture of the materials, rather than the properties of the ingredients themselves.
“These lightweight materials can withstand a load of at least 160,000 times their own weight,” LLNL engineer and lead author Xiaoyu Zheng said in a news-release. “The key to this ultrahigh stiffness is that all the micro-structural elements in this material are designed to be over constrained and do not bend under applied load.”
To produce these materials, the researchers used additive micro-manufacturing to generate 3D parts layer by layer using a variety of materials. This allowed the researchers to generate materials with micro-architectures that conventional manufacturing techniques would not traditionally be able to achieve. Perhaps one of the most impressive features of the process is that the materials were printed using a desktop machine.
The team started off by using a polymer core as a template to fabricate microlattices. They then coated this core with an ultra-thin layer of metal no more than 500 nanometers thick. By using heat to remove the polymer core, the team was left with an extremely tough yet super thin hollow tube composed of a metal lattice.
They then repeated the technique but coated the core with a 50-nanometer-thick ceramic film and the resulting material had a density similar to aerogel. Aerogels are the lightest solid materials in the world, composed of up to 99.98% air. Currently, the record holder for the world’s lightest material is aerographene.
“It’s among the lightest materials in the world,” said LLNL engineer Chris Spadaccini. “However, because of its micro-architected layout, it performs with four orders of magnitude higher stiffness than aerogel at a comparable density.”
Finally, the team employed a slightly different technique to produce a polymer-ceramic hybrid microlattice which displayed similar strength and stiffness to the other materials. The researchers boast that their novel materials are 100 times stiffer than other microlattice materials produced previously by other teams.
The researchers hope that these materials will have applications in various industries in the future, but in particular they envisage their use in the manufacture of components for cars or space vehicles.