SAMPE Journal - March/April 2021 - 15

INTRODUCTION
The demand for carbon fibre composites was estimated to be 128 thousand tonnes in 2018 and is
projected to increase to 199 thousand tonnes by
20221. This exponential demand is accompanied
by increased manufacturing and end of life wastes
that raise a lot of sustainability issues. This has stimulated the development and commercialisation of
various recycling technologies, notably the pyrolysis
process used by ELG Carbon Fibre Ltd. The products
of the pyrolytic recycling of composite waste is generally a tangled mass of carbon fibres and reproduction of a virgin fibre composite reinforcement structure is limited at a commercial scale. Currently, the
recycled fibres are chopped to approximately 80 mm
in length and is processed into discontinuous, randomly oriented non-woven mats. The efficient use
of rCF in structural and non-structural applications
could not only provide significant weight and cost
savings, but also aid in reducing the carbon fibre
waste being sent to landfill.
In order to get a firm understanding for the potential of rCF components it is important to establish their performance. vCF components are often
chosen for their superior specific fatigue resistance
and, hence, it is critical to understand the response
of rCF composites under cyclic loads. It is thus vital
to define the applicability and market for rCF based
on long term performance and environmental du-

rability. Composites are generally anisotropic and
heterogeneous in nature and damage due to fatigue can be a complex phenomenon, because they
often experience multiple locations of micro-damage simultaneously. Failure eventually occurs as
a combination of matrix damage, delaminations,
fibre-matrix debonding, void growth, interlaminar cracks and fibre breakage2. The initiation and
growth of micro cracks during its fatigue life period
leads to a continuous material softening and degradation of material properties such as its strength
and stiffness3,4. The development of damage due to
tension-tension fatigue in continuous, woven and
non-crimp textile composites, as explained experimentally5, reflects the degradation of stiffness of
samples during fatigue tests. The drop in stiffness
in unidirectional6-9, woven10-12, non-crimp5,11,13,
short fibre3,14 and discontinuous15 carbon fibre and
glass fibre composites with fatigue loading has
been widely reported and often associated with
continuous matrix deterioration and disintegration of the fibre-matrix interface16. Contrary to this
conventional notion, an experimental study on the
post-fatigue tensile behaviour of a 5-harness satin
weave CF composite showed that fatigue cycling
induced up to an 8% increase in the stiffness of the
specimens, which was explained by the straightening of the load-carrying warp yarns17. Studies on
random mat natural fibre/epoxy composites have

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SAMPE Journal - March/April 2021

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