JEC COMPOSITES MAGAZINE - Issue #136 - September/October 2020 - 23

Higher production capacity thanks to Automated manufacturing

AFP (Automated Fibre Placement) and ATP
(Automated Tape Placement) technologies.
Rohacell® HERO is able to cope with the compaction during handling or application of dry
or preimpregnated fibres/tape by unadapted
vacuum robot arms. In addition to handling
advantages, using a closed-cell foam core material also avoids the processing bottlenecks
and subsequent lengthy mould occupancy
times associated with a honeycomb core.
Feasibility studies
Two major feasibility studies focusing on
sandwich composite automatization were
completed in 2019. The Evonik team worked
on an automation project for preform production with Deutsche Zentrum fur Luft-und
Raumfahrt e.V. (DLR), the national research
centre for aeronautics and space, along with
the Airbus subsidiary Composite Technology
Centre GmbH (CTC), which specializes in
composite processing technologies. Both
CTC and DLR are located in Stade, Germany.
A separate AFP/ATP production processing
trial for the Airbus Helicopter CleanSky2
Airframe European research project, with
Evonik as the foam core partner, was also car-

Fig. 3: (a) Automated process steps for rapidly manufacturing a sandwich preform using
a machined Rohacell HERO® foam core part, as carried out on the DLR Stade EVo automated production line

ried out in Augsburg, Germany, by Fraunhofer
IGCV, the specialist institute for casting,
composite and processing technology.
The automatization feasibility studies built
upon published findings from the out-of-autoclave (OoA) hand lay-up production
study carried out by CTC back in 2014. To
provide a direct correlation with the hand
lay-up data produced in 2014, the CTC/
DLR Stade preform automatization trial was
carried out on an identical Dornier 728 nose
landing gear door made from a carbon/epoxy
prepreg composite sandwich material, with

Fig. 2: Comparison of manual and automated production * Machine and manpower ©Evonik

Rohacell® HERO once again specified instead
of the aircraft-grade honeycomb core. The
original CTC hand lay-up trial successfully
demonstrated a 25% reduction in overall
production costs, plus a 19% weight reduction
of the doors using this new material. The study
indicated that even higher reductions are
achievable with more geometrically complex
parts, as shown in Figure 1.
Honeycomb core process bottlenecks
When manufacturing a honeycomb-cored
sandwich composite component, there are
two recognized productivity problem areas
that cause major processing bottlenecks and
limit output rates. The first bottleneck is due
to the material's inherent open-cell structure,
which necessitates the use of potting materials to seal cut honeycomb core edges, and
requires the application of an adhesive film to
bond to the laminate skins.
The second bottleneck is the need for a
"two-shot" curing process to mould a honeycomb-cored laminate, which ties up tooling
during both processing stages for many hours.
To achieve higher output volumes, producers
would need to make significant capital investments in multiple sets of tooling.
Automatization investigations
To avoid these costly bottlenecks, aircraft
manufacturers are looking at alternative
high-output processing and material
solutions to replace existing honeycomb
sandwich laminate systems, including monolithic carbon fibre prepreg and thermoplastic
composite part designs. Automatization
appears to be the logical way forward for
aircraft part manufacturers given that, even
after switching from a honeycomb core to a

N°136 September - October 2020

/ jec composites magazine

JEC COMPOSITES MAGAZINE - Issue #136 - September/October 2020

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #136 - September/October 2020