JEC COMPOSITES MAGAZINE - Issue #80 - April 2013 - 45

RTM

New composite strut concept

By
Enrique Sánchez Martín Head of Composites
Manufacturing Engineering,
Helder Barros Abreu, RTM Development Engineer,
Aernnova
David Leach, Global Segment Manager Composites,
AT Aviation Henkel AG&Co. KGaA,
Chris McHugh, Technical Manager
Sigmatex (UK) Ltd.

Higher mechanical strength
Following intensive testing and iterations,
the team developed a solution which
provides 20% higher mechanical strength.
This was achieved through a systems approach using LOCTITE® BZ 9120 resin
system and LOCTITE® BZ 9900 binder
applied to the carbon fabric. The resin
system has significantly higher toughness
than state-of-the-art solutions and yet still
has a low minimum viscosity (100cps)
to enable easy infusion. The resin can be
stored at room temperature for at least six
months, reducing storage and shipping
costs. Thick parts can be manufactured

safely due to the lower heat of exotherm
compared to epoxy resins. The resin
viscosity remains stable for extended time
under infusion conditions, so that large
structures can be produced. The composite components have low flammability
and high burn through resistance.

The input of composites
Compared with existing metallic solutions
in the market, this innovative composite
strut has clear advantages in terms of
weight, corrosion and fatigue resistance.
The integration of the fitting in the RTM
process provides a highly reliable joint in
comparison with other composite struts,
allowing the use of this kind of composite component in critical applications.
Infusion technology has been shown to
provide lower-cost composite solutions
compared to prepreg. A limitation of the
technology has been the availability of
resin solutions capable of providing high
toughness and structural performance,
while still being easy to process. Although
some high toughness resins are available
they are difficult to process with high
viscosity during infusion, and are limited

Composite strut with inserted fittings concept
Can be tailored to specific customer needs

No80 April 2013 /

Feature Aeronautics

s a first step, a new composite strut
concept was developed, integrating
a carbon fibre laminate, a foam core
and two metallic fittings in a “one-shot”
RTM process. This solution has clear
advantages in terms of weight, reliability
of the fitting joint and corrosion resistance. The second step was the selection
of the best materials combination.

Struts are widely used in aircraft, mainly with the purpose
of supporting components and transferring loads between
structural components. Due to the severe structural requirements of these parts, most aircraft use metallic solutions.
Although some composite struts have been developed,
metallic bars are, to date, the choice for these applications.
Against this background, Aernnova, Henkel and Sigmatex
decided to join forces to develop a new composite solution.

jec composites magazine 45

JEC COMPOSITES MAGAZINE - Issue #80 - April 2013

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #80 - April 2013