JEC COMPOSITES MAGAZINE - EXPERT’S DIGEST - ADDITIVE MANUFACTURING - 2020 - 90

EXPERT'S DIGEST
ATL/AFP
process

Automated manufacturing of stiffened
composite shells using dry fibre material

Andreas Kolbe, Research Scientist,
Christian Krombholz, Research Scientist,
German Aerospace Center
Sven Karras, Project Leader,
Olaf Rocker, Senior Technology Manager,
CTC GmbH
Anja Haeberle, Research Assistant,
Johannes Stolz, Research Assistant,
Faserinstitut Bremen e.V.

LR mainly focused on the automated layup of DFP material. In
a first step, material-dependent
process parameters such as activation
temperature, compaction pressure
and layup speeds were evaluated in
vertical layup trials. Additionally,
material effects like bulking, fuzz balls
and tack behaviour were analysed and
considered for process and design
modifications. The challenge was the
different behaviour of dry fibre compared to prepreg material with different
defects like fuzz balls. Afterwards, CTC
focused on how to ensure a complete
infusion of the panels. Therefore, a
setup was developed that was, on one
hand, as robust as possible and, on the
other, feasible for later industrialization.
During the first trials, a direct correlation between the layup parameters and
infusion behaviour was detected and
investigated. This article describes the
trial programme, which started with a
parameter study, followed by small- and
medium-scale trials and resulting in the
large-scale part. It shows how CTC and
DLR cooperated to lay up and infuse a
large-scale part with high thickness in
an R&T environment.

Appropriate manufacturing concepts need to be developed to meet the
growing demand for CFRP parts and the increasing production rates
in the aviation sector. Therefore, a development stream is ongoing to
evaluate the potential of dry fibre placement (DFP) processes in largescale shell manufacturing. A research project funded by the NBank of
Lower Saxony concentrated on layup, infusion and curing processes
for a full-scale dry fibre material shell as part of a close collaboration
between CTC GmbH and the German Aerospace Center (DLR) in Stade.

Background
To stay competitive in the growing aircraft market, future aircraft need further
structural weight reductions that can be
achieved through the use of new materials and new manufacturing methods.
Actual R&T developments have to
focus on the reduction of recurring and
non-recurring costs, especially for a new
generation of short- and medium-range
aircraft with an estimated production
rate over 60 AC/month [1]. Therefore,
manufacturing processes with less
expensive composite and auxiliary
materials, automated and flexible plant
concepts as well as robust manufacturing methods are needed to achieve
cost benefits and a stable, appropriate
production.
As part of a large project funded by the
NBank of Lower Saxony, the major aim
was to develop and demonstrate a complete process chain for the production
of carbon fibre-reinforced plastic shells,
focusing on vertical layup, stringer
preforming and infusion process. A fullscale generic shell design was chosen as
a validator and demonstrator structure
to determine the potential, benefits and
challenges of a dry fibre process chain
for large-scale aircraft parts with high
thickness.

Expert's digest jec

State of the art
Over the past decade, production
technologies such as Automated Tape
Laying (ATL) and Automated Fibre
Placement (AFP), in combination with
preimpregnated unidirectional fibres
and autoclave curing, were established
as the standard in commercial aircraft
production. Airbus and Boeing are currently manufacturing their composite
wings for the A350 and 777X by ATL
and AFP on huge gantry machinery
with a single layup head [2,3]. The
new competitors in the short-range
sector, like the Bombardiers C-Series or
Irkut MS21, are using dry fibre. While
Bombardier is manufacturing the wing
shells in a semi-automated process with
dry fibre fabrics in combination with a
resin transfer injection process (RTI)
in an autoclave, the Russian supplier
AeroComposit uses fully-automated
Dry Fibre Placement (DFP) machinery
in combination with a membrane-assisted resin infusion process (MARI) in an
oven [4, 5, 6, 7, 8] . Compared to the
prepreg process chain, dry fibre components offer significant potential for cost
and time savings. Direct cost savings
can be expected based on less costly
processes at the material production
stage. Due to the almost unrestricted
processing time of DFP materials, the

composites magazine Additive Manufacturing

JEC COMPOSITES MAGAZINE - EXPERT’S DIGEST - ADDITIVE MANUFACTURING - 2020

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - EXPERT’S DIGEST - ADDITIVE MANUFACTURING - 2020