Billions of barrels of oil. Commuters in smog masks. Heavy metals leaching into the soil… Boats, planes and cars can have a bad reputation for environmental impact. Yet, when it comes to protecting the planet, the sustainable use of transport has a vital role to play.

At the University of Portsmouth’s School of Mechanical and Design Engineering, Professor Hom Nath Dhakal plays a leading role in making important changes happen. He’s driving pioneering research that could make the automotive, marine and aerospace industries significantly greener.

Hom is an expert in composite materials, and the leader of the University’s Advanced Materials and Manufacturing Research Group. He is breaking new ground in developing sustainable, lightweight composite materials.

Composite materials are a mainstay of manufacturing. Usually, they take the form of plastics reinforced by man-made reinforcements such as carbon fibre and glass fibres. This combination (compositing) makes the material stronger than it would be on its own.

But as Hom notes, ‘extraordinary amounts of materials have been thrown into the sea because of the problem of recycling.’

He and his team are working on a much more radical, far more natural solution – bio-composites. Hom explains:

‘We are trying to use materials that are bio-based and biodegradable after their useful life. We’re making natural composite products using plant based natural fibres as a reinforcement.

Extraordinary amounts of materials have been thrown into the sea because of the problem of recycling. 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 a reinforcement.

Professor Hom Dhakal, Professor of Mechanical Engineering

‘Flax, hemp and jute fibres are natural, renewable and abundantly available. If we can use them as reinforcements, we are talking about sustainable composites.’

There’s a pressing need to make this happen. Aside from the environmental impact of traditional composites, carbon fibres and glass fibres come from petrochemical products – which means, when the world’s oil runs out, there will be no more of them.

Plant fibres such as jute, hemp and flax are biodegradable, so industry would create significantly less landfill if it adopted sustainable bio-composites. And Hom thinks it’s possible to go a step further:

‘We want to recycle this material as much as possible so that we don’t use up our resources. If you can use waste material, that will be even better. So with that aspiration, we are trying to use waste agricultural biomass to make composites.’

Biomass is a term which describes waste material from plants, food waste and sewage, which can be used as a renewable fuel, since it is full of energy stored from the sun. Agricultural processes produce a lot of biomass as a by-product, and it’s often simply classed as waste.

As well as reducing the amount of waste that’s sent to landfill or burnt, Hom says that sustainable materials can be produced using less energy than conventional glass and carbon fibres.

It’s a potential green revolution, and one which could have very broad applications. So, how does it work?

Breaking new ground

The principle of Hom’s research is combining organic materials with plastics to create composite laminates.

The goal is to see these being used for products such as car bumpers and door linings. If you’re picturing a car partly made of plant fibres and imagining it would break if you blew on it, think again. Part of Hom’s research is about proving they have the necessary strength.

He and his team conducted several experiments to find out what happens to their materials when loads are applied. There are different mechanical properties to consider – from impact strength, to flexural strength, to fatigue - depending on what a biocomposite might be used for.

 

Flax, hemp and jute fibres are natural, renewable and abundantly available. We want to recycle this material as much as possible so that we don’t use up our resources. If you can use waste material, that will be even better. So with that aspiration, we are trying to use waste agricultural biomass to make composites.

Professor Hom Dhakal, Professor of Mechanical Engineering

The team at Portsmouth are world-leaders in their field. Hom says:

‘We are in the forefront of developing sustainable materials, specifically aiming for non-structural and structural applications.

‘We came up with a hybrid concept of putting different materials together and enhancing mechanical strength as well as other important properties.’

Strength and sustainability are not the only reasons why industry is taking notice:

‘Natural fibre composites have amazing, attractive attributes. They are lightweight, renewable and low cost.’

Manufacturing with natural fibres

As reasons for bringing biocomposites into manufacturing go, they don’t get much better or bigger than reducing the risks posed by climate change. But, if the materials developed by Hom and his team are going to make the leap to the production line, they also need to meet other industrial needs.

For example, in order to reduce emissions from vehicles, the automotive industry wants to introduce lightweight materials, so cars don’t need to burn as much fuel.

Yet 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 very strong attributes.

Light weight is a huge advantage of CFRPs. Carbon fibre is 40 per cent lighter than aluminium, and almost 60 per cent lighter than steel.

It is highly motivating for both the students and academic staff when our students get involved in research informed teaching. The manufacturing techniques they use equip them to go out into industry after they finish their course.

Professor Hom Dhakal, Professor of Mechanical Engineering

But Hom’s research suggests natural fibre reinforced biocomposites could have a real advantage here:

‘Natural fibres are a lot, lot lighter than glass fibres. The density of glass fibre, for example, is 2.5 grams per cubic centimetre. Flax is far lighter, at 1.15.

‘If you make composite panels from flax fibre compared to glass fibre, flax would consistently have very comparable specific strength and stiffness with lightness advantage.’

Hom and his team test for factors ranging from strength to endurance – for example, to find out if biocomposites can withstand harsh environments, they expose the materials to extreme hot and cold temperatures.

‘You cannot just say, okay, let’s use all natural materials. They have to fulfil a functional requirement. So, we do certain tests, follow certain standards and come up with certain values for the product – this one has amazing impact resistance behaviour, this one has very good scratch resistance property – so the industrial collaborators will be confident in using these emerging sustainable materials.’

As advanced as their research is, there are still challenges to tackle, and plenty to prove.

Overcoming obstacles

A potential drawback to using natural fibres is that they are hydrophilic materials – put simply, they absorb moisture. If exposed to humidity and moisture over a number of years, a biocomposite made with natural fibres may start to swell and lose its shape. It could also become increasingly weaker as it absorbs and retains more and more water.

So, Hom and his team are exploring treatments and processes that could make these materials more safely compatible with plastics. It’s all about achieving the mechanical strength required in a reliable, sustainable way, and minimising the risk of moisture absorption.

There’s also the challenge of setting standards and agreeing the properties of materials, before they can be adopted by industry. Hom explains:

‘Automotive manufacturers want to use materials which have 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.

‘So when you are modelling your part, you need to include a diameter, strength and density. What should this be? We have to overcome this barrier, so it will take time.’

We have to have patience and perseverance to make an impact. The challenge is getting consistent, reliable properties. It takes a long time to convince people to use a new class of materials, such as natural fibre reinforced composites for non-structural and structural applications.

Professor Hom Dhakal, Professor of Mechanical Engineering

Hom is particularly excited about the ‘amazing laminate material’ he and his colleagues have made from waste agricultural biomass. Reusable and biodegradable, it has potential to be the holy grail of composite materials. But first, there’s a lot of testing to be done:

Will it bear loads without stretching? How does it behave when bent? What happens to it in a collision?

‘It’s a long journey,’ says Hom, ‘and we have to have patience and perseverance to make an impact. The challenge is getting consistent, reliable properties. It takes a long time to convince people to use a new class of materials, such as natural fibre reinforced composites for non-structural and structural applications.’

As an active lecturer and supervisor of postgraduate research, Hom is playing a crucial part in developing a generation of young professionals who can champion sustainability in industry.

Shaping the future

Students at Portsmouth get involved in a range of Advanced Materials and Manufacturing Research Group projects. Undergrads and postgrads alike have a role to play. Hom says:

‘They are here to learn new knowledge, and here they can be exposed to the latest technology and make advanced composite materials.

‘It is highly motivating for both the students and academic staff when our students get involved in research informed teaching.

‘The manufacturing techniques they use equip them to go out into industry after they finish their course. They have got this awareness of sustainability, recycling and advanced materials that can meet engineering requirements, but at the same time cause less bother to the environment.

‘Our graduates go to industry with that message, that burning desire to use the techniques they have learned – lifecycle analysis, environmental impact assessment, environment and management systems, functional data analysis.

‘We are sending a message to industries that our graduates are capable of using these tools relating to sustainability, using materials efficiently, using less energy.’

The way we are using resources currently, we might need another 3 or 4 Earths to meet our demand. We don’t appreciate how much we have got here. So we need to do research and bring breakthroughs. We need to enhance properties and enhance the use of sustainable materials in our daily life.

Professor Hom Dhakal, Professor of Mechanical Engineering

Hom works closely with partners in industry, to make sure he and his colleagues develop innovations that solve their problems. 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.

But ultimately, his passion is not about sustaining profit generation in industry. It’s about sustaining life on our planet.

‘The way we are using resources currently, we might need another 3 or 4 Earths to meet our demand. We don’t appreciate how much we have got here.

‘So we need to do research and bring breakthroughs. We need to enhance properties and enhance the use of sustainable materials in our daily life.

‘I come to work early in the morning and go very late in order to contribute at least something to the environment I leave. Future generations will appreciate our contributions.’

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