Pastries Provide Inspiration for Layered Composites

 

Graphene and carbon nanotubes are among the strongest materials science can derive from nature. As such, engineers in the composites industry are always looking for ways to combine them with other materials to make better composites. A common tactic these days is layering one of the two materials in a matrix that is eventually cured to create the finished product.

As useful as the layering process is, it has its own drawbacks. Those drawbacks led an MIT team to start searching for a better way to layer graphene and carbon nanotubes and embed those layers in the matrix of another material. They came up with a way to do just that a couple of years ago. Interestingly enough, they looked to pastries for their inspiration.

  • Cut, Layer, Repeat

MIT researchers quickly discovered that layering graphene and carbon nanotubes is not as easy as it sounds. They discovered that the materials have a tendency to clump together because of their nanoscale size and physical properties. They had to find a way to overcome this problem without having to manually stack hundreds of layers of material.

The team looked at the way pastry chefs create their layered pastries in an efficient way that does not threaten the integrity of the dough. They observed that a pastry chef starts with a large, thin sheet of dough stretched out on a table. The sheet is folded in half, on top of itself, and cut along the folded edge. Then it is folded in half and cut again, and again, and again.

The MIT researchers decided they could use a similar process to layer graphene and carbon nanotubes. However, the fact that they were working with materials on the nanoscale meant that folding and cutting were not really practical. So they came up with a modified version of the process.

They started by creating a block of material by manually stacking layers. They then cut the block in half and slid one half on top of the other to create a stack. They then repeated the process multiple times until they had a stack that was more than 300 layers thick.

  • Making Strong Composites Stronger

So what is the practical application of the MIT research? Quite simply, it is making already strong composite materials even stronger. Consider a carbon fiber prepreg sold by Rock West Composites out in Salt Lake City, Utah. That prepreg material can be used for all sorts of manual layups.

Let’s say the prepreg’s manufacturer decided to increase the strength of the product by combining layers of graphene with carbon fibers in a matrix designed for a specific project. The graphene layers could be added to the carbon fiber fabric in two directions across the entire matrix. This would make the resulting fabric stronger than it would have otherwise been.

As an added bonus, the two-dimensional nature of graphene molecules makes the layered composite more flexible and forgiving without any reduction of strength. The finished matrix can be used to make body armor, flexible composite panels, and so forth.

MIT researchers said back in 2016 that their layering process can create a material that is better than Kevlar for some applications. More importantly, adding graphene increases matrix weight by less than 1/10 of one percent. Manufacturers do not give up any weight savings by adding the graphene.

Who knew that pastry chefs could be such an inspiration to research scientists looking for new and better ways to construct composite materials? It almost instills a greater respect for what goes on in high-in commercial kitchens. It doesn’t taste as good though.

Dean@techsophist.net'