JEC COMPOSITES MAGAZINE - Issue #80 - April 2013 - 46

RTM
The partners

Aernnova developed an innovative composite strut bar concept manufactured by
means of RTM, integrating a carbon fibre
laminate, a foam core and two metallic
inserts in a one-shot process. This patented
solution (WO 2012/085299 A1) was tested
using different materials combinations, and
the best properties were achieved with
the materials supplied by the other two
partners.
Henkel developed a family of benzoxazine
infusion resins and compatible binders.
The resins provide ease of processing with
superior mechanical performance, along
with high toughness and flammability

to moderate service temperature. In addition, reinforcements with suitable binder
systems to enable manufacture and compaction of preforms are necessary. The
integrated solution developed by the three
partners provides superior performance
in multiple areas and lower finished part
cost.

Collaborative work
The partners worked in a collaborative manner to achieve the composite
solution. Aernnova identified a strut
bar as the initial demonstrator. Henkel
developed an infusion resin and binder
system to provide superior mechanical
performance and ease of processing.
Sigmatex developed and optimized the
binder coating technology to ensure good
adherence of the binder to the fabric and

resistance. The resin can be stored at room
temperature for at least 6 months. The
multi-functional binder enables compaction
and preforming of the reinforcement, while
enhancing the interlaminar toughness of
the composite solution. The binder was
developed to allow good permeability of the
resin while avoiding wash-out during the
infusion process. Sigmatex was responsible
for weaving the carbon fabrics and coating
the binder onto the fabrics for the composite solution. Sigmatex developed and optimized the coating process so as to ensure
uniform distribution and good adhesion of
the binder to the fabric.

uniform distribution of the binder on the
fabric. The binder content can be varied
depending on the required level of interlaminar toughness and degree of preform
complexity. The development was an
iterative process to optimize all aspects of
processing and performance.

A huge market
Struts are widely used in the aeronautics
industry. The expectation is to replace
existing solutions, mainly metallic, with
this new product, taking into account the
above mentioned advantages. Infusion
solutions are being used increasingly for
composite structure due to the benefits of
lower cost, reduced assembly, and manufacture of complex integrated structure in
a single process. This solution addresses
the limitations of current materials and

Aernnova team showing fiberstruts

46 jec composites magazine / No80 April 2013

Structural test performed at Aernnova
mechanical labs

processes in the areas of cost, performance
and processing. Therefore, the innovation
opens up a much wider range of composite components to manufacture using
infusion technologies.

Key benefits
The major benefits of this very light composite strut are a reliable joint between
the inserts and the composite laminate, a
fatigue and corrosion behaviour comparable to metallic solutions and a solution
that can easily be adapted to different
structural requirements. This is also a costeffective solution due to the high degree
of part integrity in the RTM process.
This innovation increases mechanical
strength by more than 20% compared to
other composite material combinations,
reduces resin shipping and storage costs,
offers a wider infusion process window,
improves safety in the manufacture of
large components and increases the flammability and burn-through resistance.
These benefits enable greater use of infusion technologies in the manufacture of
aerospace structural components. n
More information:
www.aernnova.com
www.sigmatex.com
www.henkel.com/aerospace

http://www.aernnova.com http://www.sigmatex.com http://www.henkel.com/aerospace

JEC COMPOSITES MAGAZINE - Issue #80 - April 2013

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