JEC COMPOSITES MAGAZINE - Issue #81 - May/June 2013 - 36

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Non-destructive testing of orientation and gaps in multi-axial carbon
fibre materials without coupling media
The EddyCus CF map, utilizes the principle
of high-frequency eddy currents to test
carbon fiber composites and fabrics nondestructively. This technology is the first of its
kind. As opposed to other NdT technologies
the eddy current test has the potential to characterize carbon fiber materials at any stage
during production (roving, fabrics, tapes,
preforms and final composites). The scanner
moves an eddy current sensor across the part
and performs up to 5,000 measurements per
second. The sensor induces an electromagnetic field with a very high local resolution,
which causes eddy currents to flow within
the conductive carbon fiber bundles. This
creates a field which is then characterized
by the sensor. All measurements are then
displayed in an image, so called c-scan, which
exposes many quality characteristics of the
structures. The main benefit is to determine
structural parameters like fiber orientation,

gaps, undulation, misalignment, wrinkles,
and overlaps in hidden layers. Hence the
user can assure the quality and integrity of
the CFrP part, but also monitor and control
the production process in the future. This
enables process owners to optimize the
production process and reduce scrap. In
particular, for structurally important parts
non-destructive testing (NdT) is necessary.
The EddyCus CF map has reached industrial
stage. It is capable of scanning slightly curved
components and can be set up on top of a larger part. Soon more automation will enhance
the usability and flexibility of the system.
Manufacturers of processing equipment
as well as component manufacturers are
interested in this innovation. Particularly the
high-performance industries automotive and
aviation are potential user.
• Non-destructive test carbon fiber products (dry fabrics and composites) without

14 seat civil aircraft, ‘SARAS’ with the entire wing and empennage
developed using composites
CSIr-NAL has taken up the development
of a 14 seater civil aircraft, ‘SARAS’. For this
aircraft, the entire wing and empennage are
being developed using composites. One of
the main components of the horizontal tail
is the ‘bottom integrated skin’. The entire
bottom substructure (5.1mx1m), which
consists of the skin, 2 spars, 11 ribs and8
stringers have been co-cured in one single
operation. All the spars, ribs and stringers
were laid to the net shape on the CFrP
contoured tools. Later, these were transformed on to the already stacked skin using
the ‘specially developed locating media’ to
meet the stringent dimensional requirements. This was then vacuum bagged and
cured in an autoclave at 175 deg C and 7
bar pressure. Carbon/epoxy prepreg was
used as the basic raw material to realise the
structure. The box has successfully passed
the stringent non-destructive evaluation
(NdE) requirements) and is also meeting
the stringent dimensional tolerance requirements. The entire co-cured structure has
been developed using innovating tooling
technology consisting of ‘hybridized silicone

rubber tooling and CFrP tools’. The key
challenge was meeting the tight dimensional
tolerances, especially the radii tolerances and
an outer contour tolerance of +/- 0.5 mm.
The innovative tooling concepts included
the development of tools having the
‘required stiffness’ at the ‘required location’,
so as to ensure uniform consolidation. An
innovative vacuum bag technology has also
been developed. The main challenge in the
development of any aircraft structure is the
reduction in cost and weight. Compared
to an equivalent box in aluminium, the
weight savings was about 25%. The integral
construction not only reduced the number
of individual parts but also eliminated 2500
fasteners and resulted in a cleaner aerodynamic surface. This innovative technology has
resulted in reduction in manufacturing time
and cost from many different aspects which
include a) reduced inspection and documentation, b) fewer individual parts and
fasteners during assembly and c) reduced
usage of sealants.
The tooling developed was extremely
challenging for co-curing the ribs (with large

36 jec composites magazine / No81 May - June 2013

NDT
Winner: Suragus gmbH (germany)
Partnership Network: Fraunhofer
Institute for Non-destructive Testing in
dresden (germany)

coupling media
• Detection of gaps, misalignment, wrinkles,
overlaps and undulation, even in hidden
layers of multiaxial stacks
• Potential to assure quality across entire
value chain

Aeronautics
Winner: National Aerospace
Laboratory (India)
Partnership Network: CSIrO
(Australia)

web depth) in order to meet dimensional
accuracies, as the co-cured top skin has to be
mechanically fastened to these rib flanges.
The very first prototype parts made were
qualified for the final assembly on aircraft.
There is a huge market potential for this
innovation as it has demonstrated that it is
possible to explore co-curing technology
using composite materials for realising
large structures like the bottom skin of the
horizontal tail of an aircraft. This innovative
approach can be extended to other larger
structural parts for both military and civil
aircrafts.

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JEC COMPOSITES MAGAZINE - Issue #81 - May/June 2013

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