Residual stresses and the optimum cure cycle for an epoxy resin
Residual stresses in carbon fibre-reinforced plastic composites arise because of the large difference in thermal expansion of the fibres and matrix. It has been suggested that these stresses might be reduced in epoxy resin matrices by curing at a lower temperature. Experiments have been made on five curing cycles, to test this possibility and to study the variations of viscosity and volume changes of the resin under different cure conditions. DSC experiments have also been made to determine the degree of cure at various stages of the cycles. It was found that a cycle with the low peak temperature of 120°C required a prohibitively long length of time to produce a complete cure. Of the other cycles studied, it is predicted that it would be advantageous, in reducing residual stresses, to use a peak temperature of 160°C, rather than 175°C, provided that a dwell of 18 min is included at 160°C to ensure a complete cure.
KeywordsPolymer Viscosity Epoxy Residual Stress Thermal Expansion
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- 2.J. F. CLEMMET, Typical Examples of European Technology for High Stability Space Structures, AGARD—Requirements, Design and Development of Large Space Antenna Structures, May, 1980.Google Scholar
- 3.J. F. CLEMMET,Aerospace Dynamics September (1982) 25.Google Scholar
- 4.C. C. CHAMIS, “Lamination Residual Stresses in Cross-Plied Fibre Composites”, NASA-TM-X-52881 (1971).Google Scholar
- 5.P. L. SANDALLS, PhD thesis, University of Salford (1983).Google Scholar
- 6.J. F. CARPENTER, Instrumental Techniques for Developing Epoxy Cure Cycles, 21st National SAMPE Symposium and Exhibition, Los Angeles (1976).Google Scholar
- 7.A. R. WESTWOOD, Analysis of the Curing Reactions of Thermosetting Polymers by DSC, Proceedings of the Third International Conference on Thermal Analysis, Vol. 3, edited by H. G. Wiedemann (Birkhauser, Basel, 1972) pp. 169–77.Google Scholar
- 8.H. KAMBE, M. KOCHI, T. KATO and M. MURAKAMI, Thermal Shrinkage of High Polymers by Thermomechanical Analysis, Proceedings of the Fourth International Conference on Thermal Analysis, Vol. 2, edited by I. Buzas (Heyden, London, 1975) pp. 51–8.Google Scholar
- 9.B. YATES, B. A. McCALLA, J. P. SARGENT, K. F. ROGERS, L. N. PHILLIPS and D. M. KINGSTON-LEE,J. Mater. Sci. 13 (1978) 2217.Google Scholar