1. Development and manufacturing of cost efficient highly integrated composite structures
Christina Altkvist, Jonas Wahlbäck, Per Hallander, Tonny Nyman
Stockholm
Flygteknik 2010

2. Development and manufacturing of cost efficient highly integrated composite structures
Saab research activities has been carried out within the FP6 European project ALCAS
ALCAS – Advanced Low Cost Aircraft Structures
The objective is to reduce the operating costs of relevant European aerospace products by 15%, through the cost effective application of carbon fibre composites to aircraft primary structure, taking into account systems integration
Flygteknik 2010

3. Agenda Background Material down selection Airliner Wing Platform
Hot Drape Forming
Manufacturing Center Wing Box Rear Spar
Summary and Conclusions
Business Jet Wing Platform
Target and assumptions
Manufacturing of Sub Scale Wing Box
Testing
Cost & Weight
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4. ALCAS Overview 60 partners from 18 European countries
A total budget of million euro
Duration:
Coordinated by Airbus
Organized into four technical platforms
Airliner Wing
Airliner Fuselage
Business Jet Wing
BJ Fuselage
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5. The Airliner Wing Platform
WP1.2 Lateral Wing Box
Global Spar deformation
Saab: Analytical prediction of deformation after curing for Lateral Wing Box Rear Spar
WP1.3 Centre Wing Box
Saab: Design and cost efficient manufacturing of Centre Wing Box Rear Spar
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6. The Business Jet Wing Platform
A BJ Wing reference model was defined
Four teams - four different technologies
Partner 1
Partner 2
Saab (Sweden)
Partner 4
Saab: Design and cost efficient manufacturing of BJ Sub Scale Wing Box with high level of structural integration
Test set-up
One shot curing
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7. Material down selection
For CWB Rear spar and BJ Wing SSWB cost savings can be achieved by
Less expensive raw materials → Investigate ”non aircraft grade” carbon fiber
Innovative prepreg processing methods → Investigate ”out-of-autoclave” cure
Less expensive prepreg handling & layup → Investigate ”thick plies” and use ATL
Initial concept
Prepreg system, MTM44-1 from ACG with an out-of-autoclave process. FAW=268 g/m2
Processing trials to
determine a suitable cure cycle and investigate laminate quality when moving from thin flat laminate to thick complex structures
Back-up solution
Autoclave process with Airbus qualified prepreg system M21
Porosity problems in C-shaped spar
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8. The Airliner Wing Platform
Design, manufacturing and testing of an inner wing and centre wing box
Overall objective: 20% weight saving in the wing structure, with zero increase in recurring cost against the reference state-of-the-art metallic wing. 
Various composite materials and processes used in different components
Structural test will be carried out to validate the design
Saab: CWB rear spar
Length: 2.5 m
Web height: 0.9 m
Flange width: 300 mm
Thickness: mm
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9. Hot Drape Forming Trials
Manufacturing concept:
Flat layup of a stack of prepreg
Hot Drape Forming on male tool
Curing in autoclave
Manufacturing trials to:
develop the HDF process and to investigate influene of lay-up sequence u x
= 0
along line
corresponding
to 1% global
strain y
= 0 along line
Hot drape forming of flat laminates with fully interleaved layup was very challenging
A patch layup design preferable from a manufacturing point of view
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10. Manufacturing – Full Scale CWB Rear Spar
Design: Monolithic inward facing ‘C’ section spar with fully interleaved lay up
Integration: Bolting selected for spar to skin attachment and for stiffener to spar attachment
Material: Prepreg T800/M21
Tooling: Invar/Steel female mould tools
Process: Hand lay up on male tool. Autoclave curing in female tool.
1) Manual Lay-up
2) Set up in female tool
3) After Curing
4) Loaded into assembly jig
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11. Manufacturing Result Layup started in April 2007
Assembly completed in June 2007
Final inspection and delivery in September
Good geometrical tolerances with female tool
Waviness and porosity in some areas of the spar corners due to insufficient debulking of the lay-up
To verify the manufacturing process testing of travellers cut out from the spar was carried out.
This testing together with supporting stress analysis resulted in an approval of the rear spar.
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12. Summary and Conclusions
One piece C-spar with metal stiffener most optimal from weight- and cost point of view
Initial manufacturing with out-of-autoclave material gave raise to a high degree of porosity. Further development needed but tight time schedule made it impossible
Hot drape forming of prepreg material without wrinkles difficult in tapered areas when fully interleaved design rules applies
The female tool gives a good outer surface and the tolerance is more or less given by the spring back of the flanges. Machining of the outer surface is not needed. The height of the spar is controlled by using Invar in the web of the tool.
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13. Preamble The Business Jet Wing Platform
F7X
Preamble The Business Jet Wing Platform
Sub Scale Wing Box - SSWB
Design a composite wing box with 10 % reduced weight and 20% reduced RC compared to a metallic reference.
4 teams – 4 different approaches.
Common approach: High level of integration – less assembly.
Demonstrate each technology through manufacturing and verification.
LRI
RTM
Prepreg
”Mix”
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14. Target and assumptions
Manufacture a wing box with Skin, stringers and spars integrated and cured in one operation.
Further cost reductions:
Thick prepreg
ATL Automated Tape Laying
HDF Hot Drape Forming
Design philosophy:
No use of fasteners between upper skin and adjacent spars.
To have rigid surrounding tools and ”adjustable” internal tools.
Have Recurring Cost as top priority during the design phase.
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15. Manufacturing Lay up started In mid January. Demolding end of January.
Inspection and trimming in February.
Assembly with metallic structure from end February to end of April.
Strain Gauge installation beginning of May.
Delivery to Prague for verification mid May.
Notably: 4 month from manufacturing start to delivery.
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16. Manufacturing Result Composite Box
Prepreg solution in combination with this tool concept seems to be robust.
First attempt successful.
Geometrical tolerances acceptable.
Scale up should be possible. (Tools are low weighted)
Both tool surface and ”bag” surface of smooth condition.
Laminate quality very good.
No delaminations.
No “porosity” detected. (Edge areas)
Rear Spar difficult to manufacture due to shape.
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17. Two very satisfied engineers. (Without helmets)
Test and Test result.
Test started end of July 2009 and final testing was performed at lunch time 11 September % LL was reached without failure.
Static and fatigue.
To test the critical spar/skin splice area, artificial defects and Impact damages was introduced.
Impact damages were introduced after the limit load test. No damage propagation was detected during the fatigue load session.
The innovative design concept without fasteners between forward and rear spar and upper skin was verified by this test.
Overall good agreement between the measured and predicted strain values from FEM.
Test set up in Prague
Two very satisfied engineers. (Without helmets)
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18. Cost & Weight
Cost and Weight Assessment is on going together with Dassault and involved partners.
Initial results indicated a rather high weight but on the other hand, a very low cost which was in line with the design approach.
The initial results were “considered” to include too much company specific skills and advantages Due to this, efforts have been taken to harmonize the manufacturing values. (Common standardized values to be used for all 4 concepts)
With harmonized values it can be concluded:
The prepreg box has the lowest manufacturing cost.
The prepreg box has (together with Dassault’s LRI) the lowest weight.
Number and type of fasteners have a huge impact on the total cost.
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19. Summary & Conclusions The Business Jet Wing Platform
Composite Box
We do see a potential of this design concept specially from a cost point of view.
With a redefined design principles we believe the weight could be reduced significantly.
Assembly
The assembly cost could be reduced with use of more robotic drilling and relaxing of (harmonizing) sealing requirements.
Questions!
Thank you for your attention!
Flygteknik 2010