SOLVE magazine Issue 01 2020 - Page 15

SUSTAINABILITY AND THE ENVIRONMENT: MANUFACTURING To address this, Professor Dhakal and his team are working on a radical, but more natural, solution: biocomposites. Professor Dhakal explains: “We are trying to use materials that are biobased and biodegradable after their useful life. We’re making natural composite products using plant-based natural fibres as the reinforcement. “Flax, hemp and jute fibres are natural, renewable and abundantly available. If we can use them as reinforcements, we are talking about sustainable composites.” He says there is a pressing need to make this happen, pointing out that traditional composites come from petrochemical products, and at current consumption levels the world is estimated to only have 53 years’ supply of oil remaining. So alternative materials need to be found, with or without the environmental imperative. Of the plants that could be grown specifically for this purpose, he lists jute, hemp and flax, but adds that fibre from most crop waste – the vegetative material left after grains or fruits have been harvested – would be suitable. New technology The principle of Professor Dhakal’s research is combining organic materials with natural polymers to create composite laminates. He sees a ready use in products such as car bumpers, door linings, parcel shelves and dashboard consoles. Another crucial part of the research is proving such plant-based composites have the necessary strength. Professor Dhakal and his team have conducted several experiments in which they have put these materials under load. There are different mechanical properties to consider – from impact strength, to flexural strength, to fatigue – depending on what a biocomposite might be used for. To this end the Portsmouth team has come up with a hybrid concept of putting different materials together and enhancing mechanical strength as well as durability, but industry interest also stems from these materials being lighter and cheaper. Manufacturing with natural fibres Professor Dhakal is quite clear about the fact that for him and his team to make the leap to the production line, they also need to meet other industry needs. “For example, to reduce emissions from vehicles, the automotive industry wants lighter materials so cars in particular don’t need to burn as much fuel. “At the same time, the material must perform well in terms of its mechanical and other required properties. In aviation, for example, the Dreamliner aircraft uses around 80 per cent carbon fibre reinforced composites (CFRPs) by volume, because of their light weight and strength. Carbon fibre is 40 per cent lighter than aluminium, and almost 60 per cent lighter than steel.” Professor Dhakal’s research suggests natural-fibre-reinforced biocomposites could increase this advantage even further. “Natural fibres are a lot lighter than glass fibres. The density of glass fibre, for example, is 2.5 grams per cubic centimetre. Flax is 1.15 grams per cubic centimetre. If you make composite panels from flax fibre compared to glass fibre, flax would have comparable strength and stiffness but with a considerable weight advantage.” Overcoming obstacles The researchers are also testing other factors. To analyse biocomposites’ performance under harsh climatic conditions, they expose the materials to extreme hot and cold temperatures. “You cannot just say, okay, let’s use all-natural materials. They have to meet a functional requirement. So, we test, follow established standards and come up with specific values for the product … this one has excellent impact resistance, this one has very good scratch resistance. Industry collaborators need to be confident in using these emerging sustainable materials.” PHOTO: HELEN YATES One potential drawback to using natural fibres is that they are hydrophilic – they absorb moisture. If exposed to humidity and moisture over a number of years, a biocomposite made with natural fibres may start to lose its shape. It could also become weaker if it absorbs and retains water, which can restrict its applications. So, Professor Dhakal and his team are also exploring treatments and processes to make these materials compatible with plastic’s imperviousness. There’s also the challenge of setting materials standards: “Automotive manufacturers want to use materials with consistent properties. If you produce carbon fibre in Saudi Arabia, Canada, the USA or the UK, its diameter will be the same. But if you produce flax fibre in Canada, France or the UK, its diameter will be completely different. “We have to overcome this barrier and it will take time. It’s a long journey and it takes time to convince industries to use a new class of materials.” For this reason, Professor Dhakal is working closely with industry to keep the research aligned with its needs: “The goal isn’t knowledge for knowledge’s sake – it’s to pass on the results of research, analysis and testing, so industry can use that knowledge.” That is the pragmatist talking. Beneath this is a scientist with passion for the world around him: “Ultimately this research is about sustaining life on our planet. The way we are using up resources, we might need another three or four Earths to meet demand. So we need to do the research that enhances the use of sustainable materials in our daily life. I come to work early in the morning and leave late because I want to contribute to the environment we leave for future generations.” Flax, hemp and jute fibres are natural, renewable and abundantly available. If we can use them as reinforcements, we are talking about sustainable composites. – Hom Nath Dhakal ISSUE 1 / 2020 15