JEC COMPOSITES MAGAZINE - Issue #112 - April/May 2017 - 60
Fig. 2: Double cantilever beam (DCB) testing with the Imetrum crack length gauge
Under the European Framework 7 Clean Sky Joint Technology
Initiative , a project between Cardiff University School of
Engineering and Haydale Ltd. was funded with the aim of
developing nano-particle reinforced carbon fibre epoxy composites manufactured by resin infusion. To achieve the high
quality dispersion required, nano-carbons were functionalised using a plasma treatment process developed by Haydale
Ltd., which helps to de-agglomerate and chemically functionalise the nano-particles. The ability to controllably alter the
surface chemistry in an accurate, repeatable and scalable way
has allowed the exploration of a range of surface chemistries
and nano-carbon morphologies within this project, leading
to the best improvements in mechanical properties and manufacturability. The project has demonstrated the potential
for more consistent resin-infused nano-reinforced composite
materials to be manufactured.
Materials and manufacture
The Sika Biresin CR83 infusion resin and a medium-speed
hardener (CH83-6) were chosen as the base resin system.
This resin system has a very low viscosity (<200 mPas), long
pot life (up to 180 minutes) and room-temperature curing.
The low viscosity and long pot life are important since the
resin-infusion of low-permeability large-scale UD carbon
fibre laminates makes it challenging to achieve full wet-out.
Starting with a low viscosity resin means that an acceptable
viscosity can be maintained even with the addition of nano-fillers.
Fig. 3: Normalized properties of Haydale Ltd.
functionalised nano-reinforced composites
addition al resin and a high shear mixing technique to increase
dispersion. Reinforcement was provided by 200gsm UD carbon fibres supplied by Formax (FCIM312) in a 16-ply quasi-isotropic layup. A series of resin infusion trials were carried
out to find the optimum setup to produce test panels and
demonstrate component-scale manufacturing capability for
wing skin and I-section stiffeners. 550mm x 180mm panels
were manufactured for test coupons. Post manufacture, all the
panels were C-scanned to confirm their quality.
Materials tests were carried out to compare properties to a
standard reference composite material manufactured with
the same fibres and resin system. Compression after impact
(CAI), in-plane shear, interlaminar shear (ILSS), double cantilever beam (DCB) and tensile tests were all carried out to
evaluate the properties of the composites. Of all the test types,
compression after impact, in-plane shear and fracture toughness showed the greatest improvements.
CAI specimens were cut from manufactured panels and
subjected to 10J impacts with an Instron 9250HV, followed
Two nanocarbon morphologies were selected for reinforcement: multi-walled carbon nanotubes (MWCNT) and
few-layer graphene (FLG). The materials were supplied by
Nano-fillers were used in quantities up to 1% by volume in
the resin, first by hand mixing to 5% and then diluting with
jec composites magazine / No112 April - May 2017
Fig. 4: Component-level demonstrator (550mm x 900mm) reinforced with I-section stiffeners