Cure Cycle for Thick Glass/Epoxy Composite Laminates

Abstract

Duringthe curingprocess of thick glass/epoxy composite laminates, substantial amounts of temperature lagand overshoot at the center of the laminates is usually experienced due to the large thickness and low thermal conductivity of the glass/epoxy composites, which require a long time for full and uniform consolidation. In this work, the temperature profiles of a 20mm thick unidirectional glass/epoxy laminate duringan autoclave vacuum bag process were measured and compared with the numerically calculated results. For the calculation of distributions of the temperature, degree of cure, resin pressure, exothermic heat and required time for full consolidation by three-dimensional finite element analyses, the effects of convective heat transfer coefficient and geometry of mold and bagging assembly on the temperature profiles were taken into consideration. Based on the numerical results, an optimized cure cycle with the coolingand reheatingsteps was developed by minimizingthe objective function to reduce the temperature overshoot in the composite. From the experimental and numerical results, it was found that the measured temperature profiles were in good agreement with the numerical ones, and conventional cure cycles recommended by prepregmanufacturers for thin laminates should be modified to prevent temperature overshoot and to obtain full consolidation.

Keywords

cure cycle thick composite laminates kinetic model exothermic reaction consolidation.

Get full access to this article

View all access options for this article.

References

1. Mallick, P.K. (1988). Fiber Reinforced Composites. New York: Marcel Dekker Inc., Chapter 1.

2. Bogetti, T.A. and Gillespie, J.W. Jr. (1991). Two-dimensional cure simulation of thick thermosettingcomposites. Journal of Composite Materials, 25: 239–273.

3. Ciriscioli, P.R. , Wang, Q. and Springer, G.S. (1992). Autoclave curing – comparison of model and test results. Journal of Composite Materials, 26: 90–102.

4. Twardowski, T.E. , Lin, S.E. and Geil, P.H. (1993). Curingin thick composite laminates: Experiment and simulation. Journal of Composite Materials, 27: 216–250.

5. Hojjati, M. and Hoa, S.V. (1995). Model laws for curingof thermosettingcomposite. Journal of Composite Materials, 29: 1741–1761.

6. Michaud, D.J. , Beris, A.N. and Dhurjati, P.S. (1998). Curingbehavior of thick-sectioned RTM composites. Journal of Composite Materials, 32: 1273–1296.

7. White, S.R. and Kim, Y.K. (1996). Staged curing of composite materials. Composites Part A, 27: 219–227.

8. Yi, S. and Hilton, H.H. (1998). Effects of thermo-mechanical properties of composites on viscosity, temperature and degree of cure in thick thermosetting composite laminates during curingprocess. Journal of Composite Materials, 32: 600–622.

9. Kim, J.S. and Lee, D.G. (1997). Development of an autoclave cure cycle with coolingand reheatingsteps for thick thermoset composite laminates. Journal of Composite Materials, 31: 2264–2282.

10.

10. Young, W.B. (1995). Compacting pressure and cure cycle for processing of thick composite laminates. Composites Science and Technology, 54: 299–306.

11.

11. Blest, D.C. , Duffy, B.R. , McKee, S. and Zulkifle, A.K. (1999). Curingsimulation of thermoset composites. Composites Part A, 30: 1289–1309.

12.

12. Joshi, S.C. , Liu, X.L. and Lam, Y.C. (1999). A numerical approach to the modelingof polymer curingin fiber-reinforced composites. Composites Science and Technology, 59: 1003–1013.

13.

13. Martinez, G.M. (1991). Fast cure for thick laminated organic matrix composites. Chemical Engineering Science, 46: 439–450.

14.

14. Oh, J.H. , Kim, J.K. , Lee, D.G. and Jeong, K.S. (1999). Interlaminar shear behavior of thick carbon/epoxy composite materials. Journal of Composite Materials, 33: 2080–2115.

15.

15. Mills, A.F. (1992). Heat Transfer. Richard D. Irwin, Inc., Chap. 3.

16.

16. Lee,W.I. , Loos, A.C. and Springer, G.S. (1982). Heat of reaction, degree of cure and viscosity of hercules 3501-6 resin. Journal of Composite Materials, 16: 510–520.

17.

17. Dusi, M.R. , Lee, W.I. , Ciriscioli, P.R. and Springer, G.S. (1987). Cure kinetics and viscosity of fiberite 976 resin. Journal of Composite Materials, 21: 243–261.

18.

18. Chiao, L. and Lyon, R.E. (1990). A fundamental approach to resin cure kinetics. Journal of Composite Materials, 24: 739–752.

19.

19. Springer, G.S. and Tsai, S.W. (1967). Thermal conductivities of unidirectional materials. Journal of Composite Materials, 1: 166–173.

20.

20. Gutowski, T.G. , Cai, Z. , Bauer, S. , Boucher, D. , Kingery, J. and Wineman, S. (1987). Consolidation experiments for laminate composites. Journal of Composite Materials, 21: 650–669.

21.

21. Gutowski, T.G. , Morigaki, T. and Cai, Z. (1987). The consolidation of laminate composites. Journal of Composite Materials, 21: 172–188.

22.

22. Peters, S.T. (1998). Handbook of Composites–Second Edition. Chapman and Hall, Part One: Basic Materials.

23.

23. Kim, J.S. and Lee, D.G. (1993). On-line cure monitoringand viscosity measurement of carbon fiber epoxy composite materials. Journal of Materials Processing Technology, 37: 405–416.

24.

24. Young,W.B. (1996).Consolidation and cure simulations for laminated composites. Polymer Composites, 17: 142–148.