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
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