Composite Stacking for Strength

Researchers at the Massachusetts Institute of Technology (MIT) have developed composite materials that contain hundreds of layers, are atoms in thickness, and are evenly spaced to span the full width of the material. The discovery opens the potential to design and manufacture composites for high tech materials, optical devices, electronic systems, and more.

Many materials, like graphene and carbon nanotubes, are highly desired to reinforce composite materials, adding to their mechanical strength. But their tendency to clump together when embedded in the resin make them difficult to use effectively and at a reasonable price point. The MIT process aligns and embeds the material in the resin in an orderly fashion. Rather than folding and refolding the material over itself to create layer upon layer, they alternate layers on the nanoscale. A layer of graphene is stacked upon a composite: the block is cut into quarters that are then stacked, and the process is repeated. The result is uniform layers of composite, which the researchers say is easily and quickly embedded with the matrix material.

The team produced composites with up to 320 layers of embedded graphene. Although the amount of graphene was minimal, less than 1/10th of a percent by overall weight, it increased overall strength of the composite material.

The electrically conductive graphene layers maintain their continuity across the composite sample with no short-circuiting to adjacent layers. Inserting an electrical probe into the stack to a precise depth makes it possible to access any one of the hundreds of layers. This feature could one day lead to new types of complex multilayered electronics.

The team also found a means to create structured fibers from graphene, which could one day create yarns and fabrics with embedded electronic functions. By using a shearing mechanism, similar to a cheese slicer, they peel off a layer of graphene, causing it to roll into an Archimedean spiral. The scrolled strands, unlike flat fibers, can be woven into long fibers that could stretch without breaking.