CompTest 2011 Monitoring key parameters during the elaboration of composite parts by resin transfer moulding process (RTM) Presented by Marc WARIS 15/02/2011,

CompTest 2011

Monitoring key parameters during the elaboration of composite parts by resin transfer moulding process (RTM)

Presented byMarc 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

3

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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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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Which sensor for monitoring process

Optical fiber sensor :

Monitoring of several parameters inside the preform Which parameters can we measure?

Great tool for optimizing composite process

Advantages :

- Low dimension (250 µm diameter)

- Multiplexing several sensors

- Local measurement (in situ)

Drawbacks :

- Brittle

- Connectivity

Fiber Bragg Grating (FBG)

Fresnel principle

Two kinds of sensors

Temperature and Strain inside the preform

Output Data- to detect the resin presence

- to monitor the curing stage of thermoset resin

Development of a specific optical fiber sensor

6


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

Carbon fiber 90°

Conductor Weft

Teflon Insulator

Flaw

Good resolution

High intrusivity (600 µm)

Difficult to multiplex

Low intrusivity (125 µm)

Easy to multiplex

Limited resolution

OFS

2) Dual grating method


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Dual grating method : Two FBG inscribed side by side in the same optical fiber

Current limits :• 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 IA

FBG IIA

FBG I

1

1 1 1

2 22

2

.

B

B T

TB

B

K K T

K K


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Assessment of sensor’s sensitivity

Tested with calibrate equipment Temperature :

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

Sensivities


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Discrimination with FBG IA/ IIA

Errors analysis Theorical approach

• Errors propagation

Experimental tests• Results issued from equipment test

max 1

max 2

( , )

( , )i Ti

i Ti

T f K K

g K K

Dual-Grating sensing scheme

Temperature errors (°C/pm)

Strain errors (µε/pm)

FBG I / FBG IIA 6.32 49.8

FBG IA / FBG IIA 2.38 20.8

Interrogation system

Sensor1 2 1with pm

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)

Monitoring RTM process by OFS

1010

Case Study

Materials : Woven 48580 [902,03,902] panel 430x430x4 mm

Resin RTM 6 Mono component

RTM process and instrumentationProcess Parameters

Injection

Thermal cycle

t (min)

Ø

(cc/min)

Pl=3bar50

4 10


1111

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 - Sealed feedthrough

Easy to implement in laboratory mould

- Safety solution for industrial mould

- Accurate sensor positioning


1212

• Preparation of surface mould• Embedding of sensor in the middle of the preform

Case Study in photos

• Final part after removal from the mould• Compaction of the preform and injection


1313

Response of sensor during the process

Evolution of Bragg’s wavelength


1414


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


1515


Evolution of strain

Influence of the mould during the RTM process

360 µε induced by the mould in the cooling stage

Debonding between the part and the mould

Conclusion & Perspectives

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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

Thank you for your attention

Documents

CompTest 2011 Monitoring key parameters during the elaboration of composite parts by resin transfer moulding process (RTM) Presented by Marc WARIS 15/02/2011,