Graphene oxide can alter the properties of flax-fibre composites and make them more resistant to water, for example. This is shown in a study from Link枚ping University.
鈥淔lax fibre has a low density and offer mechanical properties suitable for some applications. Producing natural fibres requires considerably less energy than producing materials such as glass fibre鈥�, says Mohamed Loukil, Senior Associate Professor and research leader.
Graphene oxide is a nanoscale material with chemical properties that can improve the bond between the flax fibres and the epoxy in the composite material. Graphene is a strong material that can be applied in extremely thin layers, down to the atomic scale, over a surface. At the same time, this can provide excellent mechanical and barrier properties. A graphene-based coating can therefore improve the performance of natural fibres and protect them from their surroundings, for example from water and oxygen.Partners
Partners
Link枚ping University initiated the Going Green with Graphene (G3) project in collaboration with Research Institutes of Sweden (RISE), Grafren, Trifilon, electric boat manufacturer X Shore and Innovative Materials Arena (IMA). The project began in 2023 and continued as G3 Demo, during which demonstrators were built. The project concluded in June 2026.
Ulrik Svedin
鈥淲e are pleased that the study has resulted in two publications and that the research has also been presented at international conferences including ECCM 22 in Oslo, Norway, and ICCM in Baltimore, USA.. Our research on graphene and fibre composites is continuing,鈥� says Mohamed Loukil.
Flax-fibre tested in water
Khursid Malik, a postdoctoral researcher, has worked on measuring the water content of flax-fibre composites after they had been submerged in water for different lengths of time. By comparing and testing different materials and concentrations, he has shown that it is possible to reduce water absorption.
鈥淏ut there is still a big difference. Glass-fibre composites absorb very little water. That is why this research is interesting. We can investigate how far we can go with natural-fibre composites,鈥� says Khursid Malik.
Layers of composite material
The researchers tested coating the fibres with three different concentrations of graphene oxide relative to the weight of the flax fabric. The treated fibres were then used to manufacture composite laminates with a bio-based epoxy.
One of the clearest results was seen in the interlaminar shear strength, a measure of how well the layers of the composite material can withstand forces that cause them to slide relative to one another.
The shear strength increased from 16.2 MPa in the untreated composite to 20.2 MPa with 1.5 per cent graphene oxide, an improvement of around 25 per cent.
Fewer small voids
鈥淢icroscope images also showed better contact between the fibres and the epoxy, and fewer small voids in the material鈥� says Khursid Malik.
The researchers also progressed from small laboratory samples to a full-scale component for marine use. Two hatches were manufactured, one using untreated flax fibres and the other using flax fibres coated with 1.5 per cent graphene oxide.
Ulrik Svedin
A聽reduction of almost
40 per cent聽
鈥淎fter 30 days in a three per cent saline solution, the untreated hatch had absorbed around 4.8 per cent water by weight. The hatch containing graphene oxide-coated fibres absorbed around 2.9 per cent. This represents a reduction of almost 40 per cent鈥� says Khursid Malik.
But finding the right balance is important. Adding more graphene oxide did not consistently produce better results. Flexural strength increased at the lowest concentration but decreased at higher concentrations. Tensile strength also decreased as the amount of graphene oxide increased.
Coated or uncoated natural fibers
The researchers attribute this in part to local defects caused by uneven coating and accumulations of graphene oxide.
鈥淭he team aims to build on this work by developing more sustainable and automated manufacturing methods that use coated or uncoated natural fibers, depending on the application鈥� says Marie Jonsson, an associate professor at LiU and a key researcher in the project.
