Tough Carbon-Fiber Composites Inspired by Plants

Innovation: Academia

Texas A&M University

2020

Image: Jude Infantini / Unsplash / CC BY SA - Creative Commons Attribution + ShareAlike

Prevent Fracture/Rupture

High force impact or stress can cause materials that comprise living systems to separate into two or more pieces (called fracturing) or to break or burst suddenly (called rupturing). For example, a scallop prevents structural failure from fracture because its shell is comprised of two materials of varying stiffness. When a crack moves from the scallop’s stiff material to the less stiff one, the latter reduces the force at the tip of the crack, thereby stopping it from spreading farther.

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Physically Assemble Structure

Living systems use physical materials to create structures to serve as protection, insulation, and other purposes. These structures can be internal (within or attached to the system itself), such as cell membranes, shells, and fur. They can also be external (detached), such as nests, burrows, cocoons, or webs. Because physical materials are limited and the energy required to gather and create new structures is costly, living systems must use both conservatively. Therefore, they optimize the structures’ size, weight, and density. For example, weaver birds use two types of vegetation to create their nests: strong, a few stiff fibers and numerous thin fibers. Combined, they make a strong, yet flexible, nest. An example of an internal structure is a bird’s bone. The bone is comprised of a mineral matrix assembled to create strong cross-supports and a tubular outer surface filled with air to minimize weight.

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Prevent Deformation

When a living system undergoes compression, tension, shear, bending, or twisting, its internal inter-molecular forces can often resist these forces and even change shape temporarily, returning to the original shape when the forces stop. However, if the force is too strong or lasts too long, permanent deformation or structural failure can occur, resulting in death. Therefore, living systems have strategies to resist deformation or help ensure limited deformation. For example, bones have thin crystals and proteinaceous fibers that provide strength and flexibility, protecting them from forces that would otherwise cause deformation on a daily basis.

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Prevent Buckling

When a living system undergoes compression to the extent that it causes structural damage, it results in buckling. For example, if a person pushes down on the top or the side of a paper cup, the cup’s wall will eventually give way, or buckle. Although a living system could add material to strengthen a structure, this requires expending precious energy. Instead, it must use energy and materials conservatively to avoid buckling, strengthening structures through careful placement of materials to resist, absorb, or deflect compressive forces. For example, instead of one long, tubular stem, some plants like bamboo have stronger nodes scattered along their stems. When compressed, these nodes keep the round stems from taking on an oval shape that weakens the structure and could result in buckling.

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Light, strong carbon-fiber composites from Texas A&M University use recycled wood fiber to reinforce the structure while speeding up the assembly of the material.

Benefits

Durable
Lightweight
Sustainable

Applications

Manufacturing
Aerospace
Automotive

UN Sustainable Development Goals Addressed

Goal 11: Sustainable Cities & Communities
Goal 12: Responsible Production & Consumption

Bioutilization

Wood fiber

The Challenge

Polymer composites reinforced with ultra-fine strands of carbon fibers are used in many applications across industries, and are known for being incredibly strong and lightweight. Carbon nanotubes are oftentimes added to the composites to improve electrical and thermal conductivity and further increase strength. However, the chemical processes for adding the nanotubes oftentimes causes the nanoparticles to clump up and spread unevenly throughout the composite, decreasing the effectiveness.

Innovation Details

The material uses nanocrystals, derived from recycled wood fiber, to coat carbon nanotubes uniformly in the carbon-fiber composites. The cellulose nanocrystals have certain areas that attract or repel water, allowing them to anchor on to the carbon-fiber while still dispersing evenly, increasing the organization of the nanotubes and improving the composite overall.

Biological Model

Plant matter is mainly made up of cellulose, hemicellulose, and lignin. Cellulose makes up 30-50% of a plant and it’s what gives a plant its structure. It is lightweight but has a high strength to weight ratio, making it strong and durable. Cellulose can be broken down into very small components, called nanocrystals. Nanocrystals are strong and have low thermal conductivity

See Related Strategy

Biological Strategy

Nanocrystals Isolated From Cellulose Have Unique Properties

Plants

Nanocrystals isolated from cellulose are strong, flexible, and lightweight

References

Journal article

Hybrid Cellulose Nanocrystal-Bonded Carbon Nanotubes/Carbon Fiber Polymer Composites for Structural Applications

Applied Nano Materials

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