Lightweight and high-strength materials have consistently played a key role in the construction of fuel-efficient and high-performing aircraft. Today, bio-composites – made of raw materials of biological origin – are giving engineers new insight on how to improve the environmental performance of future aircraft.
Five decades ago, up to 70% of an aircraft was made of a single material: aluminum. Lightweight, inexpensive, and widely available, aluminum was used in the construction of a variety of aircraft components, from the fuselage to other main engine parts. Since then, other materials have improved aircraft design, from metals (titanium, steel, new aluminum alloys) to composites (carbon and glass fiber, polymeric and epoxy resins).
Today, a new class of highly performant materials – bio-composites – is emerging to offer more exciting possibilities for improved environmental performance as engineers aim to unlock their potential for use in future aircraft.
Bio-sourced composite materials are formed – like today’s composites – by a matrix (resin) and a fiber, but of biological origin. Increasingly used in industrial applications due to their numerous advantages, they are lightweight, flexible, cost-effective, and recyclable.
The raw materials for bio-composites are derived from natural renewable resources: biomass, plants, crops, micro-organisms, animals, minerals, and bio-wastes. Chemical and/or mechanical conversion is required to transform these raw materials into bio-composites, which can be used alone or in complement to standard materials, such as carbon and/or glass fiber.
Today, bio-composites can be composed of one or several of the following components:
Natural fibers: These fibers can be obtained from animals, plants, or minerals. They do not require a carbonization process (the conversion of an organic substance into carbon or a carbon-containing residue).
Biomass carbon fibers: Biomass (algae, cellulose, lignin) is used to create feedstock and raw materials for further transformation into fibers and resins.
Bio-resins: Resins are highly viscous substances that are converted into polymers (materials). Bio-resins are made of biological origin, derived mostly from plant oils, biomass, or bio-wastes.
In aerospace, bio-composites could be applied in the following areas:
Cabin and cargo: These applications require advanced properties relating to flammability, smoke density and toxicity (FST), and heat release.
Primary and secondary structures: These applications involve high structural loads and thus require improved mechanical performance and durability.
Auxiliary materials: These applications require functionality for non-flying materials or any means used for the production of composite components in industrial plants.
Raw materials in bio-composites
Sugar cane waste
Sugar cane waste, also known as bagasse, is a dry, pulpy material that remains after extracting juice from sugar cane stalks. Because sugar cane is widely available and a highly efficient converter of solar energy, it can yield large volumes of biomass.
Sugar cane waste is an excellent source of cellulose fibers, which can be used as filler in bio-composites. It can also be used in bio-based Furan resins, which are obtained by chemical conversion or bio-refinery. Furan bio-polymers, in combination with suitable natural or recycled fibers (such as recycled carbon fiber), could be used for aircraft interiors.
From microscopic species to large seaweeds, water algae are simple photosynthetic organisms capable of binding CO2 from the atmosphere and transferring it to biomass.
Water algae, like other biomass, could be used as a carbon feedstock to replicate the monomers used to produce today’s carbon fiber precursors or resins in standard composites. This approach could enable bio-composites to offer the same mechanical properties as existing composites for aircraft applications.
Made of volcanic rock, basalt fibers are mainly found in the lunar maria on Earth’s moon. Non-hazardous with excellent shock and fire resistance, basalt fibers have similar mechanical properties to glass fibers, but with the advantage of a simpler manufacturing process due to their less-complex composition.
Fibers produced directly from lunar rocks could be used for a variety of purposes. This includes stabilizing the 3D-printed structure of the lunar station, generating thermal insulation, improving filter systems, and providing textiles for astronaut suits.
Lightweight, fast-growing and highly elastic, bamboo is a natural composite material composed of cellulose fibers embedded in a lignin matrix.
Natural bamboo fibers combined with bio-based or standard resins could deliver many benefits. These include reducing environmental impact and improving mechanical performance.