Fibres such as flax, hemp, cellulose nanofibre, and kenaf have been used as reinforcements in composite materials for automotive applications.

A word of caution from The University of British Columbia’s Okanagan’s School of Engineering says that mould of the fungal type is proving increasingly important in the domain of engineering materials and can lead to early deterioration and structural failure.

This is especially the case as manufacturers adopt more bio-derived materials in the drive towards a greener future, explains researcher Bryn Crawford.

At UBC’s Okanagan campus, a multi-disciplinary team of researchers from the Composites Research Network and the Department of Biology, in collaboration with MIT and the National Research Council of Canada, have been studying the development and application of bio-sourced composites—specifically flax and hemp fibres.

These materials can be mixed with other materials to create cheaper, recyclable, and effective composite material products used by a range of industries, such as transportation.

In the study, researchers conducted some experiments to determine if and when mould will grow on bio-materials and how it might affect the final product. “Because we are now using biological matter, we have to think of fungal growth and how this fungal growth will affect a product’s performance,” says Crawford.

The research team examined flax and hemp fibres alongside other natural materials to determine what would happen over time to these fibres. They created ‘fibre sheets’ and then added fungi to some, water to others, and left another group of sheets untreated.

The idea of the project was to determine the types of environment where the fungal spores would grow and then test mechanical properties of the affected materials.

“We found that in both the hemp and flax fibres when no fungi were added, we still had fungi growing. When natural raw fibres are exposed to high relative humidity, mould will grow, and the potential for premature structural failure can occur.”

Susceptibility to mould growth is important for supply chains and factories to understand and manage, to ensure they are creating durable and robust products.

The team conducted a variety of tests examining them for strength, stiffness, or the amount of energy that can be absorbed before the bio-composite materials failed. They also used scanning electron microscopy to take an extreme close-up of the interior of the sample to determine fungal growth patterns, examine fractures, and failure zones.