The information in this presentation is proprietary and confidential and shall not be disclosed to or
used by a third party unless specifically authorised by the relevant GKN plc group company.
Development and Application of Thermoplastic Welded Structures
3AF – Association Aéronautique et Astronautique de France| June 13th, 2018
Michel Brethouwer GKN/Fokker Aerostructures
Lead Stress Engineer Papendrecht, The Netherlands
Proprietary and confidential restrictions on title slide apply throughout this presentation
Acknowledgements
The following persons have contributed to the information included in this presentation:
Arnt Offringa Head of R&D Department GKN/Fokker Hoogeveen (NL)
Jaap Willem van Ingen R&D Engineer GKN/Fokker Hoogeveen (NL)
Marco Doldersom R&D Engineer GKN/Fokker Hoogeveen (NL)
Johan Meuzelaar Lead Stress Engineer GKN/Fokker Papendrecht (NL)
Sylvain Chabot M&P Engineer GKN/Fokker Papendrecht (NL)
3AF – Association Aéronautique et Astronautique de France 2
Proprietary and confidential restrictions on title slide apply throughout this presentation
Overview of GKN
3AF – Association Aéronautique et Astronautique de France 3
Mexico
4 locations
China
2 locations
Landing Gear
Electrical and Wiring
Services
Aerostructures
Office locations
USA
26 locations
Netherlands
7 locations2 2 1 3
2 2
1 1
India
2 locations1 1
Romania
2 locations2
Turkey
1 location1
Belgium
1 location
Canada
1 location
1
Singapore
1 location
Thailand
1 location
United Kingdom
8 locations
1 4 3
Sweden
4 locations2
Norway
1 location
1
Germany
1 location1
Engine Systems
Transparencies
and Special Products
13 1 2 71 2
2
1
1
12015 sales
£3 billion*
Number of employees
17,000
Number of locations
62 in 15 countries
* 2015 sales include Fokker
Fokker Aerostructures
The Netherlands
Proprietary and confidential restrictions on title slide apply throughout this presentation
GKN/Fokker Aerostructures – Hoogeveen, The Netherlands
3AF – Association Aéronautique et Astronautique de France 4
Proprietary and confidential restrictions on title slide apply throughout this presentation
Characteristics of Thermoplastic Materials
Part manufacturing by consolidation is a (reversible) ‘melting’-process
Unlimited storage of pre-production material at RT-conditions
Matrix material is typically tougher than epoxies, good out-of-plane properties. Beneficial for;
GIC & CAI
Post-buckled structures & acoustic fatigue resistance
Moisture uptake is typically less than expoxies, with more favorable EKDF
Manufacturing of composite parts by;
Consolidation
Press-forming (using pre-forms)
Welding & co-consolidation
3AF – Association Aéronautique et Astronautique de France 5
Great benefit in relation to efficient part-integration:
Reduction of assembly cost and lead-time
Allows for optimized conceptual design for low weight
Proprietary and confidential restrictions on title slide apply throughout this presentation
GKN/Fokker Roadmap - Development of Thermoplastic Structures
3AF – Association Aéronautique et Astronautique de France 6
20001990 2010
A380 wing
fixed
leading
edges
First large
scale
assembly:
Welded fixed
wing leading
edges A340
Glass/PPS
First
welded
assembly:
MUC door
Fokker 50
Carbon/PPS
First
primary
structure:
bonded
GV
pressure
floors
First series
production:
press-formed
Dornier ribs
Carbon/PEI
First co-
consolidated
torsion box,
AW169
First Induction
welded
control
surfaces,
G650
Carbon/PPS
Co-consoli-
dated floor
beam
Carbon/PEKK
Ca/PEKK
CS2 ALFA
NLF HTP C/PEKK Demonstrator
2012 2018
Induction
welded
control
surfaces,
Falcon
Business Jet
Single Aisle
Rudder Skin
C/PEKK HTP Stiffened Skin
C/PEKK Fuselage Panel
Conduction Welded Frames
Proprietary and confidential restrictions on title slide apply throughout this presentation
Welding of Thermoplastic Materials
The welding of thermoplastic structures allows;
Reduction or elimination of costly mechanical fasteners:
No drilling & countersinking of holes
No placement of fasteners
More weight optimized conceptual design
The following thermoplastic welding processes are applied at Fokker;
Ultrasonic welding
Resistance welding
Induction welding
The following thermoplastic welding processes are currently under development at Fokker;
Conduction welding
Resistance welding 2.0
3AF – Association Aéronautique et Astronautique de France 7
Proprietary and confidential restrictions on title slide apply throughout this presentation
Ultrasonic Welding
Main applications:
Fast joining of inserts to CFRP Floorpanels
Ply fixation during hand lay-up of Glass/PPS semi-preg plies
Features:
Established and robust technology
Locally applied, less suited for long welds
3AF – Association Aéronautique et Astronautique de France 8
Proprietary and confidential restrictions on title slide apply throughout this presentation
Ultrasonic Welding – Joining of Inserts
3AF – Association Aéronautique et Astronautique de France 9
Joining of inserts to CFRP Floorpanels
Proprietary and confidential restrictions on title slide apply throughout this presentation
Ultrasonic Welding – Ply Fixation during Hand Lay-Up
3AF – Association Aéronautique et Astronautique de France 10
Accurate ply positioning using
Laser Projection System (LPS)
Ply fixation using ultrasonic ‘point’-welding
Proprietary and confidential restrictions on title slide apply throughout this presentation
Resistance Welding
Main applications:
Airbus A340-500/600 Fixed Leading Edge J-Nose (inboard section)
Airbus A380-800 Fixed Leading Edge J-Nose (mid / outboard sections)
Features:
Joining of non-electrical conductive materials;
Thermoplastic glass material
Thermoplastic carbon material with insulation between heating element and carbon fibers
Heating element: metallic grid or wire at joint-interface heated by an electric current
Weld-line can be curved but weld-length is currently limited (electric voltage limitation)
Foreign material (metallic wire) remains at joint interface
Simple welding equipment
3AF – Association Aéronautique et Astronautique de France 11
Proprietary and confidential restrictions on title slide apply throughout this presentation
Resistance Welding
3AF – Association Aéronautique et Astronautique de France 12
+
-Glass laminate
Weld strip
Weld pressure
Electric current
Glass/PPS Rib
Glass/PPS Skin
Weld-strip is placed between the thermoplastic parts
Electric current heats the joint from the inside
Weld-strip remains in the welded joint
No further rivets are required
(except at weld-ends where applicable)
Proprietary and confidential restrictions on title slide apply throughout this presentation
Resistance Welding at Fokker: In Production Since 2000
3AF – Association Aéronautique et Astronautique de France 13
A380-800
Fixed Leading Edge J-Nose
Significant weight reduction achieved against acceptable cost-level
Proprietary and confidential restrictions on title slide apply throughout this presentation
Resistance Welding process: A380 FLE J-Nose
3AF – Association Aéronautique et Astronautique de France 14
Welding of multi-rib stiffened Leading
Edge Skin;
Joining of Glass/PPS Ribs and Skin
Simple welding equipment
Curved weld-line
No bolts needed
Elimination of shimming
Proprietary and confidential restrictions on title slide apply throughout this presentation
A380-800 Fixed Leading Edge J-Nose Assembled to Wing
3AF – Association Aéronautique et Astronautique de France 15
Fixed Leading Edge J-Nose
A380-800
Proprietary and confidential restrictions on title slide apply throughout this presentation
Resistance Welding of Carbon/PPS: Development
3AF – Association Aéronautique et Astronautique de France 16
+
-Carbon Laminate
Insulated Weld Strip
Carbon/PPS Rib
Carbon/PPS Skin
Insulated weld-strip
Welded joint
Due to electric conductivity of carbon, electric insulation of
weld-strip is required to prevent short-circuit (current leakage)
Most robust solution developed: insulation of metallic mesh
weld-strip with glass-layers
Drawbacks of this solution;
Welding-strip is difficult to industrialize due to cost
Additional glass-insulation layers add weight to the joint
Applied to single Fokker 50 MUC, not further industrialized
Proprietary and confidential restrictions on title slide apply throughout this presentation
Induction Welding
Main applications:
Gulfstream G650 Elevators & Rudder
Dassault Falcon F6X Elevators & Rudder
Features:
Based on KVE Composites Group patented technology liscensed to Fokker, industrialized by Fokker
Material to be welded requires to be electrically conductive with resistive nodes (fiber-crossings)
Heating element: induction head (coil / ‘torch’) to deliver an alternating magnetic field at weld area
Magnetic field induces an alternating current in the carbon fabric creating resistive heating allowing the
thermoplastic parts to fuse together
No foreign material at joint interface (no inclusion of separate welding-strip)
No contact between heating element and material (no imprint visible after welding)
No weld-length limitation
Highly automated process significantly reducing assembly cost, but more complex and heavy weld-tooling
3AF – Association Aéronautique et Astronautique de France 17
Proprietary and confidential restrictions on title slide apply throughout this presentation
Induction Welding
3AF – Association Aéronautique et Astronautique de France 18
Generated
heat
Alternating
current in
C/PPS
laminate
Induction coil
C/PPS
laminate
Alternating magnetic field induces alternating current in
laminate
Alternating current generates heat within carbon fabric
due to joule heating (resistive heating)
Weld direction
Temperature vs time in a weld
0
50
100
150
200
250
300
350
400
0 25 50 75 100 125 150 175 200
Time [sec]
Tem
pera
ture
[oC
]
14C/s
5C/s
2C/s
2C/s
Resistance weld
Induction weld
Temperature vs time in a weld
0
50
100
150
200
250
300
350
400
0 25 50 75 100 125 150 175 200
Time [sec]
Tem
pera
ture
[oC
]
14C/s
5C/s
2C/s
2C/s
Resistance weld
Induction weld
Time [sec]
0 25 50 75 100 125 150 175 200
400
350
300
250
200
150
100
50
0
Tem
per
atu
re[º
C]
Temperature vs time in a weld
Resistance weld
Induction weld
Time [sec]Tem
pera
ture
[ºC
]
Temp vs time in a weld
Proprietary and confidential restrictions on title slide apply throughout this presentation
Research on Induction Welding of Carbon/PPS (2006 – 2008)
3AF – Association Aéronautique et Astronautique de France 19
A KVE Composites Group patented induction weld set-up was used to perform research on feasibility on induction welding technology on thermoplastic Carbon/PPS moveable structures
No metal weld strip
C/PPS skin
C/PPS rib
Proprietary and confidential restrictions on title slide apply throughout this presentation
Research on Induction Welding of Carbon/PPS (2007)
3AF – Association Aéronautique et Astronautique de France 20
A typical Torsion-Box section 1.2 [m] x 0.7 [m] was designed and built
Feasibility was successfully demonstrated and it was decided implement the induction welding technology as joining method for Carbon/PPS Moveable Torsion-Box Parts
KVE Composite Group weld technology was licensed to Fokker
Proprietary and confidential restrictions on title slide apply throughout this presentation
Induction Welding Tool Principle
3AF – Association Aéronautique et Astronautique de France
Weld jig contour boards contain
slots for the induction coil at rib and
beam positions
The contour boards define the
outside of the product
The rib or beam is pressurized from
the inside
The coil is moved by a robot
A heat sink cools the outside of the
skin
Proprietary and confidential restrictions on title slide apply throughout this presentation
Industrialized Full-Scale Development – Business Jets Moveables
3AF – Association Aéronautique et Astronautique de France 22
Robot installed on a 24 [m] track
Fully automated welding process
Significant assembly lead-time reduction per ship-set
Proprietary and confidential restrictions on title slide apply throughout this presentation
Optimal Conceptual Design of Elevators & Rudder
High torsional stiffness;
Control surface effectivity
Flutter behavior
Low bending stiffness;
Low hinge interface loads (as a result of enforced displacement by HTP or VTP)
Sufficiently high to tolerate single hinge-failure
Low weight;
Multiple rib chordwise stiffened post-buckled thin skin with stable sub-structure allows weight
efficient compliance to the above conceptual requirements;
Post-buckled skin reduces bending stiffness (occurence of shear-buckles above flight loads)
Chordwise stiffnening maintains aerodynamic profile
Shear stiffness is maintained
Challenge to produce such a multiple-part concept against acceptable assembly cost and lead-time
3AF – Association Aéronautique et Astronautique de France 23
Proprietary and confidential restrictions on title slide apply throughout this presentation
Optimal Conceptual Design of Elevators & Rudder
3AF – Association Aéronautique et Astronautique de France 24
Highly automated induction
welding of ribs and spars to skins
C/PPS Spars: Autoclave
consolidation on male tool
C/PPS Skins:
Autoclave consolidation
C/PPS Ribs:
Press-formed flat laminates
Press
Industrialized automated induction
welding assembly tooling
Proprietary and confidential restrictions on title slide apply throughout this presentation
Optimal Conceptual Design of Elevators & Rudder
3AF – Association Aéronautique et Astronautique de France 25
C/PPS induction welded Torsion-Box:
1. Torsion-Box Skins
2. Front Spar
3. Rear Spar
4. Torsion-Box Ribs
C/PPS removable bolted parts:
5. Leading Edge
6. Trailaing Edge
Aluminium parts:
7. Leading Edge Ribs
8. Hinge / Actuator Brackets
9. Hinge Brackets
Proprietary and confidential restrictions on title slide apply throughout this presentation
Parameters Influencing Quality of Induction Weld
Heating profile during welding process;
Weld peak-temperature to achieve good melting conditions
Specific window of temperature & time to obtain good entanglement of the PPS chains
Cooling-down rate of weld-bath to achieve semi-crystalline PPS
Weld-bath position relative to web / radius of rib;
Weld-bath center corresponds to position of induction coil (guided by weld-tooling in all directions)
Weld-bath width is a function of temperature
Gaps between the parts before welding;
Welding process can accomodate different gaps during welding to a certain extent
This control accurate assembly dimension after welding
Flanges of internal parts are pressured form inside
Skin controlled by contour boards on outside
3AF – Association Aéronautique et Astronautique de France 26
Proprietary and confidential restrictions on title slide apply throughout this presentation
Heating Profile During Welding Process
3AF – Association Aéronautique et Astronautique de France 27
Weld-peak temperature
(to achieve good melting conditions)
Window of temperature & time
(to obtain good entanglement of PPS chains)
Cooling-down rate
(to achieve semi-crystalline PPS)
Proprietary and confidential restrictions on title slide apply throughout this presentation
Effect of Weld Temperature on Weld-Bath Width
3AF – Association Aéronautique et Astronautique de France 28
Relation between weld-bath width
and weld peak-temperature
Weld-bath width measurement example: phased-array
scan of an induction weld (with thermo-couples)
Proprietary and confidential restrictions on title slide apply throughout this presentation
Full-Scale Welding Qualification Test
After released weld-tool and equipment available;
Pre-production component is manufactured
Thermo-couples are installed in each weld (around 5 per weld)
All weld recipes are verified by measuring and recording weld temperatures
After welding, full assembly is NDI scanned and melt-bath is measured
Coupons are machined from pre-production component and strength tested in peel to verify weld-strength
and process
After successful manufacturing & confirmation the weld-process is qualified for series production
3AF – Association Aéronautique et Astronautique de France 29
C-Scan of Rudder Rib-to-Skin welded
joints including thermo-couples
Proprietary and confidential restrictions on title slide apply throughout this presentation
Quality Control of Induction Welding in Series Production
NDI;
100% NDI is performed on all welds
Recording of coil power consumption and weld-speed per weld
Relationship between weld-bath width and temperature is used, i.e. weld-bath width is measured through
NDI as demonstration of suffient applied temperature and weld-joint integrity
In-Process control: Test welds on regular (sampling) basis are performed to monitor process over
time to detect unknown variables and demonstrate consistent weld-strength and process
3AF – Association Aéronautique et Astronautique de France 30
Proprietary and confidential restrictions on title slide apply throughout this presentation
Test-Pyramide Welded Joints: Carbon/PPS
3AF – Association Aéronautique et Astronautique de France 31
Sonic Fatigue ‘shaker’ Tests
Peel & Shear Welded Joint
Static & Fatigue Tests
Lightning-Strike Test
Full-Scale Component Test
Open Hole, CAI &
Single Lap-Shear Tests
Fokker approved material
Qualification by supplier
Coupon Level
Element Level
Detail Level
Sub-Component Level
Component Level
Lamina & constituents (fiber / resin)
Proprietary and confidential restrictions on title slide apply throughout this presentation
Conduction Welding – Under Development
Targeted applications (in research status):
Thermoplastic Carbon/PEKK Fuselage Panels with welded frames
Thermoplastic Carbon/PEKK Moveables (Flaps & Control Surfaces)
Features:
Also applicable to thermoplastic Carbon UD-tape material (in addition to fabrics)
Heated stamp: provides external heating and pressure
No foreign material at joint interface (no inclusion of separate welding-strip)
Contact between heating element and material
Tooling requires more space-envelope (to apply heat & pressure)
Potential for highly automated process significantly reducing assembly cost
3AF – Association Aéronautique et Astronautique de France 32
Proprietary and confidential restrictions on title slide apply throughout this presentation
Conduction welding
C/PEKK: Ortho-Grid Fuselage Panels
3AF – Association Aéronautique et Astronautique de France 33
Automated Fiber Placement of Skin (AFP) Ortho-grid fuselage panelCo-consolidated butt-joint
Proprietary and confidential restrictions on title slide apply throughout this presentation
Conduction Welding of Frame to Ortho-Grid Panel
3AF – Association Aéronautique et Astronautique de France 34
Grid Blade-Stringer
Ortho-grid fuselage panel
Frame
Automated conduction welding process
Welded frame to ortho-grid panel,
no additional fastners added
Proprietary and confidential restrictions on title slide apply throughout this presentation
Possible Future Applications of Conduction Welding
3AF – Association Aéronautique et Astronautique de France 35
Welding of rib- and spar
webs to ortho-grid skins
Proprietary and confidential restrictions on title slide apply throughout this presentation
Summary & Conclusions
3AF – Association Aéronautique et Astronautique de France 36
Application of composite structures offers opportunities to weight optimize conceptual designs,
but traditionally came at a higher cost
Innovative solutions have been and must be continuously developed to reduce part-
manufacturing cost and assembly cost & lead-time
Application of thermoplastic materials can support the realization of optimized conceptual
designs at acceptable cost-levels;
Unlimited storage at room-temperature, no clean room required
Cost efficient production of high part-counts by press-forming, i.e. stiffeners and ribs
Good out-of-plane properties and more favorable EKDF
Cost efficient integration of parts by means of co-consolidation & automated welding processes
Further development of welding technologies ongoing
Thermoplastic composite materials are maturing from secondary structure to primary structure
Challenge: expand application of thermoplastic materials on primary structures