The schematic illustrates engineered materials with composite layers. Carbon fiber layers (long silver tubes) interspersed with "carbon nanotube forests (brown object arrays)".
Image Source: American Association for the Advancement of Science website
Engineers at MIT have demonstrated that they can prevent cracks from propagating between layers of composite materials using a newly developed nanoscale stitching method. By depositing chemically grown "carbon nanotube forests" between the layers of composite materials, tiny and densely packed fibers tightly secure each layer together, akin to super-strong nylon fasteners, preventing delamination or shearing of the layers. The related research was published on the American Association for the Advancement of Science website on the 18th.
In a quest to save fuel and reduce aircraft emissions, researchers are seeking to manufacture lighter, stronger aircraft using advanced composite materials. These composites are made from high-performance fibers embedded within polymer sheets, which can be stacked and pressed into multilayered materials, resulting in extremely lightweight and durable structures.
However, composite materials have a weakness: the spaces between layers typically require polymer "glue" to bond the layers together. If an impact occurs, cracks can easily propagate between the layers and weaken the material's strength. Over time, composite materials may suddenly fail without warning.
The team's experiments on thin layers of carbon fiber laminate plates showed that the crack resistance of the material increased by 60% compared to traditional polymer composites when the layers were bonded via nanoscale stitching.
The concept of nanoscale stitching involves "planting" vertically aligned "carbon nanotube forests" – hollow carbon fibers. Each carbon nanotube is so small that billions of them can stand in an area smaller than a fingernail. To grow the nanotubes, the team used a chemical vapor deposition process to deposit carbon as tiny supports on the surface. These supports are eventually removed, leaving behind a dense "carbon forest canopy".
Researchers envision that any vehicle or structure employing traditional composite materials could become lighter, tougher, and more resilient through nanoscale stitching. The next generation of aircraft, if combined with composite materials and nanoscale stitching technology, could become safer and have a longer lifespan.
