JEC COMPOSITES MAGAZINE - Issue #80 - April 2013 - 54

CAE tools
About RUAG

RUAG is an international technology group in the aerospace and
defence sectors headquartered in Bern (Switzerland). RUAG has
production sites in Switzerland, Germany, Austria, Hungary, Sweden,
and the USA, and employs 7,700 people worldwide, of which 5,000
are in Switzerland, including 10% trainees.

Tab. 1: Summary of the relative effort involved in conventional and DMU
methods

Conventional

Full DMU

Relative effort

3D design

calculate the local fibre orientation. By defining acceptable
limit values for the directional deviation, the tool generates a
graphical output where the out-of-limit areas are highlighted.
Fibre direction is corrected by dividing lamina/plies into
several plies and reorienting the individual plies.
The seed strategy defines at which point and in which
primary direction the ply is laid in the mould. The local
drape of the fabric obviously depends on the seed strategy.
The CAD tools can also analyse the ply drape depending on
the seed strategy. The limit angles individually determined
beforehand for every type of fabric applied are considered
and a graphical output is produced (Fig. 3).
Wrinkles are prevented either by partially (or completely)
cutting plies or by adapting the lay-up strategy for individual
plies. Since seed point and seed line are also considered in
the drape simulation, different lay-up strategies can be simulated within the design process, rather than during the manufacturing of prototype laminates. Without modern composite CAD tools, the lay-up strategy was elaborated during the
manufacturing of the prototype part, being a time-consuming trial and error process that often resulted in scrap parts.
When drape simulation was not possible, an alternative to
prevent wrinkles was to choose a “conservative” lay-up, resulting in a higher number of cut pieces and therefore in a more
expensive manufacturing process with higher material costs
(mainly due to more residual fabric material).

Task

Lamina
represented as
non-functional
surfaces

Fully parameterized plies

+ 60%

Direct import of
Manual definition
fully parameteof ply properties
rized 3D model

- 50 %

Generation of FE
model
Generation of
manufacturing data

2D design

Export of cutter/
laser data

- 50 %

Definition of seed
strategy

Shop experience,
trial and error

Defined with
the DMU

- 90%

Nesting

Physical master
plates

Automated

- 20%

Lay-up (recurring)

Drawings/jigs

Laser guided

Up to - 80%

Industrialization and manufacturing
The manufacturing data is generated as soon as the design
and analysis of the composite part are completed. Following
the classical development process, this step means producing
drawings for the individual plies, summarized in so-called
ply books and section drawings illustrating the lay-up.
Flat patterns were traditionally evaluated by putting foils
into the mould and copying cut-section lines from the
mould to the foil. Since foils do not drape, the resulting flat
patterns were inherently inaccurate. Corrections then had to
be applied on the initial ply cuts. Overall, the manufacturing
process was a time-consuming, challenging and error-prone
task.
With the use of modern composite CAD tools, this process
has been dramatically improved in terms of effort and quality. The cutter data required to cut the plies is directly obtained from the DMU, similar to the generation of CNC data
for machined metallic parts. Before exporting the data, the
three-dimensional shape of the plies is flattened, respecting
the drape. Modern computerized numerical control (CNC)

54 jec composites magazine / No80 April 2013

Fig. 4: Unmoulding of a large sandwich structure for space application

fabric cutters can also label the plies with their identification
and nest the plies optimally considering the fibre orientation. The effort for establishing drawings is then limited to
overview drawings for documentary purposes.
Laser projectors are used for the physical lay-up of the plies
in the mould. The contour of the ply, seed point and line are
projected into the mould, as well as the ply identification.
Optical referencing systems are used for the relative orientation of the laser projector to the mould.
It has been found that the use of modern CAE/CAM tools
massively shortens the time required to generate manufacturing data, cut the plies and form the lay-up. Table 1 gives
an indication on the effort saved. The accuracy of the flat
pattern was found to be very good. n
More information:
www.ruag.com

http://www.ruag.com

JEC COMPOSITES MAGAZINE - Issue #80 - April 2013

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