PhD Candidate: Huajie Shi
Department: ASM
Section: Structural Integrity & Composites
Supervisor: I.F. Villegas, H.E.N. Bersee
Promoter: M.J.L. van Tooren
Start date: 05-10-2009
Funding: CSC, TAPAS project
Cooperations: Fokker, Airbus
Resistance welding of
thermoplastic composites
Background
Research outline
Progress 3: Process induced voids
Thermosetting and thermoplastic polymers are two kinds
of matrix for fibre reinforced polymer (FRP) composites.
Compared
with
thermosetting
composites
(TSC),
thermoplastic composites (TPC) are more environmentally
friendly for both manufacturing and recycling processes.
Compared with mechanical joining and adhesive bonding
techniques, resistance welding has been regarded as a
more suitable joining techniques for TPCs, and it has
already been applied in the aircraft industry for secondary
structures, i.e. the fixed leading edges of A380. In order to
apply TPCs for the primary structural components such as
fuselage and wings, key technologies related to the
manufacturing of TPCs are being developed in the frame of
TAPAS project.
Therefore, in order to utilize resistance welding for primary
TPCs structure, higher level knowledge of the welding
mechanisms should be known.
Combining process modelling and experimental tests in the
analysis, investigations are performed at levels of material,
process and structure.
An investigation on the process induced voids/porosities,
i.e. residual volatile induced voids and fibre de-compaction
induced voids, is performed.
Material
 Effect of fibre orientation
 Effect of fibre-matrix
adhesion
 Effect of heating element
65x
Structure
Process
 Heat transfer analysis
 Consolidation, deconsolidation analysis
 Effect of heating time
and cooling rate
 Process control method
 LSS, ILSS, TTT tests,
failure mode analysis
 Stress/strain analysis
 Fracture toughness
analysis
With voids
No voids
Progress 1: Welding process model
Progress 4: Welds quality optimization
Transient heat transfer models are developed for both
static resistance welding and continuous resistance
welding, based on which welding mechanisms such as
consolidation, crystallization and squeezing flow are also
looked into.
In order to improve the mechanical performance of the
welds, the effect of heating time, heating element, fibre
orientation and fibre-matrix adhesion on the welds quality
is studied.
The temperature distribution from edge to center
at 12mm clamping distance
500
450
Temperature (degC)
400
Schematic drawing of resistance welding setup
A
B
350
300
2mm clamping
distance
6mm clamping
distance
9mm clamping
distance
12mm clamping
distance
250
200
150
100
50
0
0
10
20
30
40
50
60
70
80
45X
45X
2mm
2mm
17mm
Heating element
Heating element
90
13mm
13mm
X-coordinate from left edge of the laminate (mm)
Tailored heating element
The temperature distribution on the overlap
direction
400
350
Temperature (degC)
300
250
d = 2mm
d = 1mm
d = 0mm
d = -1mm
d = -2mm
200
150
100
50
0
Source: Fokker Aerostructures, the Netherlands
0
2
4
6
8
10
12
14
Overlap length, d (mm)
Objectives
Progress 2: Welds quality characterization
Progress 5: Process control
The objective of this study is to investigate the
mechanisms of the welding and reveal the relationships
between material properties, welding process and the
welds performance.
In order to assess the quality of the resistance welded
structures, reliable testing method should be selected.
Therefore, various mechanical testing methods are
employed and compared.
A welding quality control strategy for resistance welding
process is proposed by detecting and utilizing the weldthickness evolution.
Displacement curve (80kW-130s)
500
Test 1
Test 2
Test 3
Displacement average
Temperature
140
120
100
80
400
300
200
60
40
100
20
Processing window
0
0
50
100
150
0
200
250
300
Welding time (s)
Single lap shear
test
-0.0018
Resistance welding setup (developed in TUD)
Transverse tensile
test
exy
Digital image correlation test
Lap shear strength
40
Short beam shear test
35
0.005
C-scan inspection
28.65
30
32.04
31.56
28.32
28.06
24.79
25
20
30.92
22.21
21.04
16.72
15
Processing window
10
5
0
30
35
40
45
55
65
80
90
100
Welding time (s)
Publications
- Shi H, Villegas IF, Bersee HEN. Effect of Fibre-Matrix Adhesion and Fibre orientation on Thermoplastic Composite Welded Joints. SAMPE 2013. Long Beach, CA, USA. May 6-9, 2013.
- Shi H, Villegas IF, Bersee HEN. An investigation on the strain distribution of resistance welded thermoplastic composite joints. 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural
Dynamics, and Materials Conference. Honolulu, Hawaii, USA. Apr 23-26, 2012.
- Villegas IF, Shi H, Bersee HEN. Processing Windows For Resistance Welding of Thermoplastic Composites: What Lies Underneath? ECCM 15. Venice, Italy. Jun 24-28, 2012.
- Shi H, F.Villegas I, Bersee HEN. Modelling of Heat Transfer and Consolidation for Thermoplastic Composites Resistance Welding. ICCM 18. Jeju, South Korea. Aug 21-26, 2011
120
Temperature ( C)
DCB test
Displacement (μm)
160
Lap shear strength (MPa)
Aerospace Engineering
Voids