In order to support the ecological transition, many companies are developing their business in the use of new, more environmentally friendly materials.
Used in many fields, composites are currently mainly reinforced with non-bio-based fibres, such as glass or carbon, which have a high environmental impact. Natural-origin alternatives are now available and becoming more widely used, such as flax and basalt. Other materials, such as bamboo or hemp, are also of interest, but their supply chains are less developed, resulting in more limited sourcing and less established knowledge of manufacturing processes.
Flax fiber
Grown 80% in France through agriculture requiring little pesticide and water, flax is bio-based, recyclable and biodegradable. Its processing is simple and involves only three stages: scutching, spinning and weaving. As a result, its production requires little energy, approximately 5 times less than glass fibre and 25 times less than carbon fibre. However, its environmental impact depends greatly on where the processing takes place. A large part of flax spinning is currently carried out in Asia, giving it a significant carbon footprint, mainly due to transport. However, some stakeholders are seeking to relocate these services, which would considerably reduce this issue and provide a cleaner material. For example, the company Safilin recently opened its first spinning mill in northern France. Production traceability is therefore essential. In addition, throughout its growth, flax absorbs CO2 — around 250,000 tonnes per year in France — giving it a negative carbon footprint if this parameter is taken into account.
In addition to its environmental benefits, flax fibre offers many other advantages. First of all, it is the strongest cultivated plant fibre. With good fatigue behaviour, higher specific stiffness than glass fibre and a lower density (1.5 compared with 2.5), it offers very strong potential for use in a wide range of sectors. It is increasingly found in automotive bumpers and crash structures. Flax has a high elongation at break, giving it excellent shock absorption capacity. To further improve its mechanical properties, it can be hybridised with carbon fibres, providing a compromise between performance and environmental responsibility.
Finally, flax is also interesting from an aesthetic point of view thanks to its distinctive appearance, which differs from other composites and gives it a more traditional and natural character. All these characteristics explain the significant development this sustainable material has experienced in recent years.
Basalt fiber
Basalt is a volcanic rock. Through the rapid cooling of magma in contact with water or air, this rock acquires high mechanical properties. At a similar density, basalt fibre has much higher tensile strength and elastic modulus than glass fibre.
It is particularly well suited to extreme conditions thanks to its excellent resistance to fire, high temperatures, radiation and corrosion. Performing well in ballistic applications, it is therefore beginning to be used for bulletproof vests and military vehicles. Another advantage of this material is the very low level of smoke released in the event of a fire, which can greatly improve safety in various fields.
However, the main benefit of basalt lies in its environmental impact. Bio-based and recyclable, its extraction and processing require little energy, giving it a low carbon footprint, close to that of glass fibres.
In recent years, a new fibre has been developed by the company Isomatex. Composed of various volcanic rocks, their Filava product offers higher mechanical properties and a higher service temperature than traditional basalt, while retaining its other advantages.
Environmentally friendly and high-performing, volcanic rock fibres could eventually replace glass or carbon fibres in many applications.