Pure Mode I,II and Mixed Mode Interlaminar Fracture of Graphite/Epoxy Composite Materials

Abstract

Pure mode I, II and mixed mode fracture tests were performed to characterize the delamination of unidirectional graphite/epoxy composite. Double cantilever beam specimens were used for the pure mode I test and end loaded split specimens were used for the pure mode II test. The critical strain energy release rates were evaluated by beam theory and compliance method and the values were 333 J/m² and 1105 J/m² respectively. Modified mixed mode bending tests were performed to investigate the mixed mode I/II delamination. Various mixed mode ratios could be produced by simply changing the applied load position on the loading lever and the bending load position on the specimen. A new analytical method was presented that can decompose the total strain energy release rate into mode I and mode II components. Experimental and finite element results agreed well with the theoretical ones.

Keywords

delamination mixed mode fracture graphite/epoxy strain energy release rate

References

1. Hashemi, S. , Kinloch, A.J. and Williams, J.G. , 1990, “The Effects of Geometry, Rate and Temperature on the Mode I, Mode II and Mixed-Mode I/II Interlaminar Fracture of Carbon-Fibre/Poly(ether-ether ketone) Composites,” J. of Composite Materials, Vol. 24, pp. 918-955.

2. Hunston, D.L. and Bascom, W.D. , 1983, “Effects of Lay-up, Temperature, and Loading Rate in Double Cantilever Beam Tests of Interlaminar Crack Growth,” Composites Technology and Review, Vol. 5, pp. 118-119.

3. Aliyu, A.A. and Daniel, I.M. , 1985, “Effects of Strain Rate on Delamination Fracture Toughness of Graphite/Epoxy,” ASTM STP 876, pp. 336-348.

4. Daniel, I.M. , Shareef, I. and Aliyu, A.A. , 1985, “Rate Effects of Delamination Fracture Toughness of Graphite/Epoxy,” ASTM STP of Symposium on Toughened Composites.

5. Carlsson, L.A. , Gillespie, J.W., Jr. and Pipes, R.B. , 1986, “On the Analysis and Design of the End Notched Flexure (ENF) Specimen for Mode II Testing,” J. of Composite Materials, Vol. 20, pp. 594-605.

6. Mall, S. and Kochhar, N.K. , 1986, “Finite Element Analysis of End Notch Flexure Specimens,” J. of Composites Technology & Research, Vol. 8, No. 2, pp. 54-57.

7. Wang, Y. and Williams, J. G. , 1991, “Correction Factors for Mode II Interlaminar Toughness Tests (ELS and ELF),” Proc. 8th Int. Conference on Composite Materials, ICCM-8, Honolulu.

8. Williams, J.G. , 1988, “On the Calculation of Energy Release Rates for Cracked Laminates,” International Journal of Fracture, Vol. 36, pp. 101-119.

9. Wilkins, D.J. , Eisenmann, J.R. , Camin, R.A. , Margolis, W.S. and Benson, R.A. , 1982, “Characterizing Delamination Growth in Graphite/Epoxy,” ASTM STP 775, pp. 168-183.

10.

10. Rankumar, R.L. and Whitcomb, J.D. , 1985, “Characterization of Mode I and Mixed-Mode Delamination Growth in T300/5208 Graphite/Epoxy,” ASTM STP 876, pp. 315-335.

11.

11. Rybicki, E.F. , Hernandez, T.D. , Deibler, J.E. , Knight, R.C. and Vinson, S.S. , 1987, “Mode I and Mixed Mode Energy Release Rate Values for Delamination of Graphite/Epoxy Test Specimens,” J. of Composite Materials, Vol. 21, pp. 105-123.

12.

12. Hashemi, S. , Kinloch, A.J. and Williams, J.G. , 1987, “Interlaminar Fracture of Composite Materials,” Proc. VI Int. Conference on Composite Materials, ICCM-VI, London, pp. 254-264.

13.

13. You, H. and Yum, Y.J. , 1997, “Loading Rate Effect on Mode I Interlaminar Fracture of Carbon/Epoxy Composite,” J. of Reinforced Plastics and Composites, Vol. 16, No. 6, pp. 537-549.

14.

14. Yum, Y.J. and You, H. , 1999, “Strain Energy Release Rate of Carbon/Epoxy Composite Material under Mixed Mode Delamination,” J. of the Korean Society for Composite Materials, Vol. 12, No. 3, pp. 66-74.

15.

15. Yum, Y.J. and You, H. , 1999, “Analysis of Mixed Mode Interlaminar Fracture in Carbon/Epoxy Composite Material,” Proc. of 10th International Pacific Conference on Automotive Engineering, SAE.

16.

16. Hahn, H.T. , 1983, “A Mixed Mode Fracture Criteria for Composite Materials,” Composite Technology Review, Vol. 5, pp. 26-29.