Optimization of pultrusion process parameters for flax fibre – reinforced thermoplastic composite tape production
L. Impelluso (TU Delft - Mechanical Engineering)
G.A. Filonenko – Graduation committee member (TU Delft - Team Georgy Filonenko)
Kunal Masania – Mentor (TU Delft - Group Masania)
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Abstract
Thermoplastic matrices reinforced with natural fibres offer a promising solution toward the
development of sustainable composite materials, which provide the potential for recyclability
while lowering environmental impact. This research is particularly relevant to the growing
sustainability concerns about WTBs (Wind Turbine Blades), predominantly manufactured from
thermoset composites that are very difficult to recycle. These present huge EoL challenges due
to the inability to efficiently process decommissioned WTBs, often leading to landfilling or
energy-intensive recycling methods. In such a context, this work addresses the development of
f
lax fibre-reinforced thermoplastic composite tapes via a lab-scale vertical pultrusion process.
The focus will be to optimize melt pool temperature, pulling speed, and die geometry for high
quality, recyclable composites that are suitable for wind energy applications.
A custom machine was designed and produced to allow the combination of flax fibre twisted
yarns and melted thermoplastic to make composite tapes by pultrusion. The influences of some
key variables, for instance, consolidating die length, pulling speed, and processing temperature,
on surface texture, void content, and fibre impregnation were studied. The results indicated that
using a shorter consolidating die along with higher pulling speeds and high pultrusion
temperatures, caused increased surface roughness. However, with an increase in the yarn count
to reduce the gap between the fibres, the surface texture for the samples treated at 190°C
(highest temperature tested) was significantly reduced.
Ultrasonic welding was also done, followed by lap shear tests to evaluate the weldability and
mechanical strength of the tapes produced with the vertical pultrusion setup compared to
benchmark samples. It was noted that the tapes processed at 190°C showed better mechanical
properties compared to tapes processed at 170°C, which could be related to better fibre
impregnation and higher crystallinity of tapes. Overall, the testing of welded samples showed that
the mechanical properties of pultruded tapes were significantly superior compared to
benchmark samples, as a result of stronger fibre-matrix bonding and considerably higher surface
quality.
Future work should focus on refining die designs to further explore the effect of long tapered die
sections, performing detailed crystallinity analyses, and employing advanced void measurement
techniques.