JEC COMPOSITES MAGAZINE - Issue #89 - May 2014 - 39

MSN 1 first flight

Implementing "GRID"
to design wing covers
The rationale to improve and the
advent of "GRID"
Initial attempts to obtain in the design
stage adequately accurate interfacing
surfaces with composite design software
were difficult and involved a lot of
"engineering license". Corrections,
which involved some re-surfacing work
due to the lack of quality of the 3D
model, proved very demanding and time

consuming.
The first available composite design tools
used on the A400M developed a dubious
reputation among the engineering design
community; even the resulting mass
properties raised serious doubts about the
weight prediction accuracy of the software
toolset.
At the same time, the final assembly line
demanded higher accuracy of the parts
in order to reduce their cycle time. The
"GRID" design methodology promised to
deliver all the necessary improvements.

Designing the A350 wing covers
using the "GRID approach"
Initial reluctance by some in the design
community was due mainly to human
factors: resistance to change and relying
on methodology that had already been
proven in previous aircraft programs.
After some coaching, the design teams
embraced with confidence the efficiency
that the new process promised. Weight
predictions, which resulted from the
enhanced design methodology, also
were more credible. Both covers, upper
and lower, were fully defined using the
"GRID" approach; some other primary
structures, such as the front and rear wing
spars, were also similarly defined.

Conclusions
The experience acquired in all aspects of
composite design and manufacture technology during the last 40 years enabled
Airbus to be at the forefront of aircraft
design and integration.
The technological breakthrough in accurate composite design is relatively recent.
The shortfalls identified in composite part
design technology in previous aircraft
programmes convinced Airbus of the
need to implement, yet again, a substantial
improvement in this field. The joint effort
with Dassault resulted in an advanced
composite design toolset, which is used
on the A350 XWB by Airbus, suppliers
and elsewhere when the need arises to
generate nominally accurate 3D models.
Efficient industrial processes rely on
precise building blocks. The accurate definition of the design data set has positive
repercussions downstream in the process,
which will translate into superior aircraft
performance. n

Results
At the time of writing (5/2013), three
No89 May 2014 /

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Feature Aeronautics

the design toolset and the design data
set required to drive the robots.
Hand lay-up was the norm during the
early days; production rate was limited
and secondary structural parts generally
had a limited number of plies. The first
inroads in automated tape laying (ATL)
occurred when larger primary structures were introduced (VTP, HTP).
The A320 pioneered ATL at Airbus.
Advanced fibre placement (AFP) was
then introduced on the A380 and
geometrically complex AFP parts (wing
spars) were introduced on the A350.
The trend at Airbus is to rely ever more
on robot accuracy and higher deposition
rates together with specialized processes
such as resin infusion techniques, using
higher modulus carbon fibres, and stamping/forming techniques with thermoplastic resins.

wing sets have been joined to their fuselages and MSN3 wings are in jig nearly
complete and ready to be delivered to the
FAL.
There are still some further minor
improvements required to the composite
part design toolset. The ultimate aim is to
deliver accurate parts derived from accurate 3D models. The Airbus partnership
with Dassault has been invaluable to
provide user feedback to further refine the
software.
For the wing covers, the overall process
spans activities from design to manufacturing and assembly. It starts with sizing, followed by automated transfer of thickness
data from the stress to the design toolset.
The design data set is utilized to drive the
numerically-controlled ATL robots and
for the precise placement of the formed
stringers which are co-bonded to the skin.
Edge trimming, inspection, painting and
drilling also rely on the accuracy of the
design data set.

jec composites magazine 39

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JEC COMPOSITES MAGAZINE - Issue #89 - May 2014

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #89 - May 2014