Monitoring Parameters in Resin Transfer Moulding Process (RTM)

1. CompTest 2011 Monitoring key parameters during the elaboration of composite parts by resin transfer moulding process (RTM)Presented byMarc WARIS15/02/2011, Lausanne (Switzerland)B. Tortech, E. Marin, A. Vautrin

2. Outline • Context and process monitoring • Development of a specific Optical Fiber Sensor (OFS) • Monitoring Resin Transfer Moulding process (RTM) by OFS • Conclusions and perspectives

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)

4. 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 4

5. Fiber Bragg Grating (FBG) Fresnel principle Two kinds of sensors - to detect the resin presence - to monitor the curing stage of thermoset resin Output Data Temperature and Strain inside the preform 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 5

6. OFS Insulator Teflon Flaw Weft Conductor Carbon fiber 90° 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 2) Dual grating method 1) temperature compensation with a thermocouple Low intrusivity (125 µm) Easy to multiplex Limited resolution Good resolution High intrusivity (600 µm) Difficult to multiplex

7. Development of a specific optical fiber sensor • 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 IIA FBG IA FBG I 7

8. Assessment of sensor’s sensitivity • Tested with calibrate equipment • Temperature : Sensivities 8

9. Discrimination with FBG IA/ IIA • Errors analysis • Theorical approach • Errors propagation • Experimental tests • Results issued from equipment test Interrogation system Sensor Increase of errors caused by : - Some problem with equipment test (homogeneity of temperature along the fiber) - slow Interrogation system (1 min for one spectrum) 9

10. Ø (cc/min) 50 Pl=3bar t (min) 4 10 Case Study • Materials : • Woven 48580 [902,03,902]panel 430x430x4 mm • Resin RTM 6 Mono component • RTM process and instrumentation 10

11. 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 - Sealed feedthrough - Groove with sealant - Safety solution for industrial mould - Accurate sensor positioning Easy to implement in laboratory mould 11

12. Case Study in photos • Compaction of the preform and injection • Preparation of surface mould • Embedding of sensor in the middle of the preform • Final part after removal from the mould 12

13. Response of sensor during the process • Evolution of Bragg’s wavelength 13

14. 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 14

15. 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 15

16. 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 16

17. Thank you for your attention