Transcript Comptest 2011 Waris

CompTest 2011
Monitoring key parameters during the elaboration
of composite parts by resin transfer moulding process (RTM)
Presented by
Marc WARIS
15/02/2011, Lausanne (Switzerland)
B. Tortech, E. Marin, A. Vautrin
Outline
• Context and process monitoring
• Development of a specific Optical Fiber
Sensor (OFS)
• Monitoring Resin Transfer Moulding
process (RTM) by OFS
• Conclusions and perspectives
Context and process monitoring
Context
 Development of LCM process for complex part manufacturing (Project LCM
Smart)
 Today Empirical Approach
 Realization of trial, geometric compensation mould
 Problematics:
• the time and the cost development increase
• No information on the sensibility of the process
 Towards a more scientific Approach
 Development of the process knowledge through appropriated instrumentation
 Modeling of the process
First steps
- Development of a specific optical fiber sensor (OFS)
- Feasibility assessment of the instrumentation process
(RTM)
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Context and process monitoring
Why monitoring Resin Transfer Moulding Process (RTM)
 To reduce the number of scrap parts
 To have a better knowledge of the process :
 Tooling design (Injection strategy)
 Find the suitable parameters
 To reduce the time development of new part
Reduction development cost
 To control the evolution of physical parameter during the elaboration
 Evolution of temperature and strain inside the part
• Control of the thermal cycle
 Control of the cure degree evolution
• Control of the time process cycle
 Detection of the flow front
• Control of the filling stage
Process improvement and their reliability
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Context and process monitoring
Which sensor for monitoring process
 Optical fiber sensor :
Advantages :
- Low dimension (250 µm diameter)
- Multiplexing several sensors
- Local measurement (in situ)
Drawbacks :
- Brittle
- Connectivity
 Monitoring of several parameters inside the preform
 Which parameters can we measure?
Two kinds of sensors
Fiber Bragg Grating
(FBG)
Output
Data
Temperature and Strain inside the
preform
Fresnel principle
- to detect the resin presence
- to monitor the curing stage of thermoset resin
 Great tool for optimizing composite process
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Development of a specific optical fiber sensor
Development of a specific optical fiber sensor
 Objectives :
 Assessment of the temperature and the strain with a resolution of 1°C and
around 50 µε respectively
 Minimizing the intrusivity of sensor
 Problematic :
 Discrimination of the temperature and the strain
1) temperature compensation with a
thermocouple
Good resolution
Teflon
Insulator
2) Dual grating method
OFS
Low intrusivity (125 µm)
High intrusivity (600 µm)
Easy to multiplex
Difficult to multiplex
Limited resolution
Flaw
Conductor
Weft
Carbon fiber
90°
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Development of a specific optical fiber sensor
Development of a specific optical fiber sensor
 Dual grating method :
 Two FBG inscribed side by side in the same optical fiber
 B1 
  
K
 B1    T 1
 B 2   KT 2
  
 B2 
 Current limits :
K 1   T 
.
K 2    
• the conditionement of the matrix K
• the resolution of Bragg’s wavelength measure
 Dual grating with different types of FBG :
 FBG type I, IA and IIA
• Different sensitivities to the temperature
FBG IIA
FBG IA
FBG I
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Development of a specific optical fiber sensor
Assessment of sensor’s sensitivity
 Tested with calibrate equipment
 Temperature :
Sensivities
Grating
KT(pm/°C)
Kε(pm/µε)
FBG I
9.97
1.28
FBG IA
9.67
1.28
FBG IIA
10.43
1.31
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Development of a specific optical fiber sensor
Discrimination with FBG IA/ IIA
 Errors analysis
 Theorical approach
• Errors propagation
 Tmax   f ( K i , KTi )  1 
     g ( K , K )   
i
Ti  
2
 max  
Sensor
 Experimental tests
•
Dual-Grating sensing
scheme
Interrogation
system
Temperature errors
(°C/pm)
Strain errors
(µε/pm)
FBG I / FBG IIA
6.32
49.8
FBG IA / FBG IIA
2.38
20.8
with 1  2  1 pm
Results issued from equipment test
Dual-Grating
sensing scheme
Temperature
errors (°C)
Strain
errors (µε)
FBG IA / FBG IIA
8
120
Increase of errors caused by :
- Some problem with equipment test (homogeneity
of temperature along the fiber)
- slow Interrogation system (1 min for one
spectrum)
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Monitoring RTM process by OFS
Case Study
 Materials :
 Woven 48580 [902,03,902] panel 430x430x4 mm
 Resin RTM 6 Mono component
 RTM process and instrumentation
Process Parameters
Injection
Ø
(cc/min)
50
Pl=3bar
4
10
t (min)
Thermal cycle
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Monitoring RTM process by OFS
Embedded sensor in rigid tool
 RTM process harsh environment
 High compaction of reinforcement
 Relative High Pressure of injection (3 bars)
 Shrinkage of the resin in the injection channel
 Some requirements
 Good alignment of optical fiber inside the preform
 Perfect seal between the optical fiber and the mould
 Two solutions
- Groove with sealant
Easy to implement in
laboratory mould
- Sealed feedthrough
- Safety solution for
industrial mould
- Accurate sensor
positioning
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Monitoring RTM process by OFS
Case Study in photos
• Compaction
ofsensor
the preform
Preparation
Embedding
Final
part after
of
of
surface
removal
inmould
from
theand
middle
theinjection
mould
of the preform
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Monitoring RTM process by OFS
Response of sensor during the process
 Evolution of Bragg’s wavelength
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Monitoring RTM process by OFS
Response of sensor during the process
 Evolution of the temperature
- We noticed no variation of
Bragg’s Wavelength during
the injection
 No detection of the flow
front
- No exothermic phenomena
measured
 thin plate
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Monitoring RTM process by OFS
Response of sensor during the process
 Evolution of strain
Debonding between
the part and the
mould
 Influence of the mould during the RTM process
 360 µε induced by the mould in the cooling stage
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Conclusion & Perspectives
Conclusions & Perspectives
 Dual grating method is a good way to discriminate the temperature and the
strain
 Easy to multiplex several sensor along the same fiber
 Less intrusive than a sensor with temperature compensation
 Validation of RTM process instrumentation with reference model parts
 Application of the OFS to complex shaped parts :
 manufacturing of thick part and thickness variation
 influence of process parameters upon the quality of the final part
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Thank you for your attention