Swedish national arena for lightweight innovations Cost-efficient structural composite parts combining unidirectional tape reinforcements and injection molding processes Dominik Stapf Deputy Head Composites & Joining Technologies, IWK Rapperswil
Swedish national arena for lightweight innovations
Cost-efficient structural composite parts combiningunidirectional tape reinforcements and injection
molding processes
Dominik StapfDeputy Head Composites & Joining Technologies, IWK Rapperswil
Agenda
◼ Introduction Institute for Materials Technology and Plastics Processing (IWK)
◼ Process Injection molded components with UD-tape reinforcement
◼ Challenge Part
High-Performance ring shaped Element
◼ Challenge 50% lighter
Fiber reinforcement why - and why not ? (https://www.duden.de/rechtschreibung/Feder)
◼ Challenge 50% costs
Efficiency and Performance by combining two processes (https://www.wjtv.com/top-stories)
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HSR Hochschule für Technik Rapperswil
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https://de.wikipedia.org/wiki/Datei:Switzerland_in_Europe.svg https://www.google.com/maps
IWK Institute for Materials Technology and Plastics Processing
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Interfaces and surfacesPolymer engineering
Light weight
design
Hybrid technologyIntegration of
functions and
processes
Simulation
Biobased plastics
Mechanics/
Kinematics
(2005)
Metal Processing
(2016)
Compounding/
Extrusion (2010)
Joining
technologies
(2015)
Composites/
Light weight
design (2015)
Fields of InnovationAdditive Manufacturing
Injection
Moulding/
Polyurethane
(2005)
IWK Institute for Materials Technology and Plastics Processing
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Challenge
Challenge – High Performance parts
Efficiency
Ressources
Performance
Costs
Automotive
Consumer
Sports
Public transport
Industry
Medical
Complexity of the parts
Performance
Weight
Costs
Lightweight structural parts
https://www.juraprofi.de
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HYX Mold
Challenge – High Performance parts
◼ Challenges of a thin-walled part for automotive application
◼ Static pressure-loaded
◼ Very high reliability
◼ Long lifecycle
◼ 100 % tightness against fluids is essential
◼ Hot/wet conditions in service
◼ Efficiency and function – big lot size, easy to mount
◼ Integration of functions
◼ Corrosion resistance
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9
Challenge 50 % Lighter
Metals
NonreinforcedPlastics
Short-fiberreinforcedPlastics
ContinousreinforcedPlastics
Weight Mechanical Performance
Challenge 50% LIGHTER
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Aluminum 2.7 g/cm3
Fiber reinforced plastics (50 % FVC) 1.4 g/cm3
50 % LIGHTER
Challenge 50% LIGHTER
Shaping Plastics
◼ geometric requirements
◼ Integration of functions
Long fiber reinforcement
◼ mechanical requirements
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https://www.easycomposites.co.uk
Aluminum
Challenge 50% LIGHTER
◼ High strength of glass or carbon fibers: 1.7-7 Gpa(high-alloyed steel max. 2.0 GPa)
◼ High stiffness of carbon fibers: 230-700 GPa (steel 210 GPa)
◼ Low density of composites materials: 1.5-2.0 gr./cm3
(steel 7.5 gr./cm3)
◼ High potential with regard to integration of functions/geometry in a broad variety of production processes
◼ Very good fatigue behavior
◼ Corrosion resistance of composite materials
◼ Specific strength:
◼ Specific stiffness:
12
3
B
cm/g
MPa=
3cm/g
GPaE=
Exemplary calculation for different layer sequences
(Assumptions: Young’s Modulus fiber: 230GPa; approx. 60% fiber volume content)
Layer sequence
Young’s Modulus
in 0°
[GPa]
Density
[g/cm3]
Spec. Young’s
Modulus
[GPa/g cm-3]
Cross section view
CFK-UD (0°) 142 1.5 94
CFK-biax. (0/90°) 76 1.5 51
CFK-quasi-iso. (0/60/-60°) 54 1.5 36
Aluminium 72 2.7 26
Challenge 50% LIGHTER
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100%
54%
38%
100%
51%
54%
38%
28% Composite: 10% weight savings
Challenge 50% LIGHTER
◼ The appropriate uniaxial (or
even biaxial) stresses seem
very limiting.
◼ In fact, a lot of suitable
applications exists.
◼ The fibers have to be oriented
in a way taking into account
the flow of forces.
◼ However, 3-axial, fast
changing stress states are
not suited in general.
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FF
MM+
-
Challenge 50% LIGHTER
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Strength
Stiffness
Impact
Weight
DesignFreedom
Lot size
Continous-fiberreinforcement
Thermoplastics
Thermoplastic Materials
+ High mechanical performance
+ Low weight
+ Great design freedom
+ Fast processing times
Challenge 50% LIGHTER
Short fibre reinforced Long fibre reinforced Continuous fibre reinforced
Fibre length 0.3-2mm, random 5-50mm, random >50mm, oriented
Typical stiffness <20GPa <30GPa <380GPa
Typical strength <220MPa <350MPa <2200MPa
Geometry Complex parts Shell like parts Depending on process
Process • Injection molding
• Low material costs
• High lot sizes
• Automated
• Press processes
• Low material costs
• Medium lot sizes
• Automated
• Various processes
• High material costs
• Small lot sized
• Labour-intensive
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Challenge 50% LIGHTER
◼ The combination of
excellent mechanical
properties and high
lot sizes is still
challenging with
composites
◼ In general, cycle times
remain relatively high
towards the top end of
the mechanical
properties
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Me
ch
. p
rop
ert
ies
Lot size
Prepreg-
Autoclave
Infusion
RTM
Hand
laminationSMC
GMT
Pultrusion
Injection
moldinglow
me
diu
mh
igh
Up to 1’000 approx. 10’000 from 100’000
BMCExtrusion
Winding
Casting
Structural components
?
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Challenge 50 % costs
Challenge 50% Costs
◼ The combination of
excellent mechanical
properties and high
lot sizes is still
challenging with
composites
◼ In general, cycle times
remain relatively high
towards the top end of
the mechanical
properties
19
Me
ch
. p
rop
ert
ies
Lot size
Prepreg-
Autoclave
Infusion
RTM
Hand
laminationSMC
GMT
Pultrusion
Injection
moldinglow
me
diu
mh
igh
Up to 1’000 approx. 10’000 from 100’000
BMCExtrusion
Winding
Casting
Structural components
Injection
molding
(short fibres)
Injection
molding (UD-
Tapes)
Challenge 50% Costs
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1. Pick up insert
2. (Preheat insert)
3. Transfer to mold
4. (Thermoforming)
5. Back injection
6. Remove from mold
1 2
3
45
6
GranulesUD-Tape
https://www.kraussmaffei.com/imm-en/fiberform.html
Challenge 50% Costs
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◼ Mechanical Testing with specialized tools
◼ Application of inner pressure by conical punching tool
→ Compression strength of the part
→ Strength at the joining of the circular tape
→ Comparison with results from simulation and optimization
Challenge 50% Costs
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◼ Optimization of tape joint is
done by FEA
◼ The manufactured samples
are tested in a quasi-static
setup (punching tool)
◼ Dependent on the joint
design, the failure mode
changes from delamination
to fiber fracture
◼ Hydrolysis effects have to be
taken into account
Bu
rst p
ressu
rein
[b
ar]
Delamination vs. fiber fracture
0
50
100
150
200
0 5
str
ess in N
/mm
2
stroke in mm
INFLUENCE OF HYDROLYSIS EFFECTS ON TENSILE STRENGTH
effected byhydrolysis
no hydrolysiseffects
Challenge 50% Costs
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◼ The adhesion between tape and thermoplast
depends on several process parameters:
◼ Combination of materials
◼ Tool and material temperature
◼ Flow path and mold design
◼ A perfect bond has to be achieved for optimal
mechanical properties
injection Surface next to injection point
cohesive fracture in thermoplast
Surface far away from injection point
adhesive fracture between tape and
thermoplast
Inner layer
THERMOPLASTIC
POLYMER
Outer layer
UD-TAPE
Challenge 50% Costs
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BACK-INJECTION OF UD-TAPES RESIN-TRANSFER-MOULDING
resinhardener
Moulding
injection
curing/
cross-linking
upper die
lower die
finish: grinding,
polishing, painting
demoulding
tempering
preheating
cutting to sizefibre
material
layer
lay-up
scrap
assembling
preforming
trimming
upper die
lower diehold-down
dry preforms
thermoplastic
resin
TP-UD-Tape
cutting to size
fixed mould half
ejector mould half
UD-Tape-pre-
cut placing
back-injection
of the UD-
Tape /cooling
ejection
sprue
removal
Not necessary
Some seconds
Some minutes
Not necessary
cleaning
Challenge 50% Costs
◼ Back-injection of UD-Tapes combines the excellent
mechanical properties of the tape with the short cycles
times of injection molding
◼ Structural components become feasible (overcome
limitation of injection molding material)
◼ High lot sizes and reasonable costs become feasible
(overcome limitation of typical composites)
◼ Complex parts are feasible
◼ The unidirectional properties have to be considered when
designing a component
◼ There is a wide variety of materials and applications
◼ Fatigue life and ageing is limiting some applications
◼ Due to the automation potential, a production of such
components is possible in Switzerland
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Strength
Stiffness
ImpactWeight
DesignFreedom
Metals
Continous fiber reinforced plastics
Thermoplastics
Challenge 50% Costs
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◼50% Lighter
◼ Replacement of Metals by continous fiber
reinforcement
50% Costs
Replacement of RTM process by injection
moulding + Long fiber reinforcement
Challenge 50% Costs
13. Rapperswiler Kunststoff Forum
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Swedish national arena for lightweight innovations
Thank you for your attention !
Dominik Stapf
Institute for Materials Technology and Plastics Processing (IWK)
+41 (0) 55 222 4766