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

Abstract

A detailed study on the interlaminar failure of carbon-fibre/poly(ether-ether ketone) unidirectional composite (termed PEEK composite: "APC-2" from ICI (UK) plc) is presented. A fracture mechanics approach has been adopted and Mode I, Mixed-Mode I/II and Mode II tests have been conducted and the effects of specimen geometry, test rate and test temperature have been investigated. It is shown that for the interlaminar fracture of the PEEK composite the value of the interlaminar fracture energy, G,, generally in creases as the crack propagates through the composite, i.e., a rising "R-curve" is observed. Thus, it is not usually possible to assign one unique value to the interlaminar fracture energy, G_c, for any given Mode of loading for the PEEK composite. We have therefore defined both an initiation value, G_c (init), and a steady-state propagation value, G_c (s/s prop). The variation of these parameters with the Mode of loading, method of precracking and the test temperature is described in detail. From optical and electron microscopy studies it is shown that in Mode I the "R-curve" behaviour mainly arises from the degree of fibre-bridging increasing as the interlaminar crack grows, whilst in Mode II it appears to mainly arise from the increasing degree of microcracking and plastic deformation damage which develops around the tip of the advancing crack. The failure loci for the in terlaminar fracture of the PEEK composite have also been established, and various theo retical models to describe these data are considered.

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References

Devitt, D.F. , R.A. Schapery and W.L. Bradley. 1980. "A Method for Determining the Mode I Delamination Fracture Toughness of Elastic and Viscoelastic Composite Materials," J. Composite Materials, 14:271.

Bascom, W.D. , J. L. Bitner, R.J. Moulton and A.R. Siebert. 1980. "The Interlaminar Fracture of Organic-Matrix Woven Reinforced Composites ," Composites, 11:9.

Whitney, J.M. , C.E. Browning and W. Hoogsteden. 1982. "A Double Cantilever Beam Test for Characterising Mode I Delamination of Composite Materials," J. Reinforced Plastics and Composites , 1:297.

Keary, P.E. , L. B. Ilcewicz, C. Shaar and J. Trostle . 1985. "Mode I Interlaminar Fracture Toughness of Composites Using Slender Double Cantilevered Beam Specimens," J. Composite Materials, 19:154.

Aliyu, A.A. and I.M. Daniel. 1985. "Effects of Strain Rate on Delamination Toughness of Graphite/Epoxy," Delamination and Debonding of Materials, ASTM STP 876, p. 336.

Russell, A.J. and K.N. Street. 1985. "Moisture and Temperature Effects on the Mixed-Mode Delamination Fracture of Unidirectional Graphite/Epoxy ," Delamination and Debonding of Materials , ASTM STP 876, p. 349.

Carlsson, L.A. , J. W. GIllespie and B.R. Trethewey. 1986. "Mode II Interlaminar Fracture of Graphite/Epoxy and Graphite/PEEK ," J. Reinforced Plastics and Composites, 5:170.

Smiley, A.J. and R.B. Pipes. 1987. "Rate Effects on Mode I Interlaminar Fracture Toughness in Composite Materials," J. Composite Materials, 21:670.

Leach, D.C. , D.C. Curtis and D.R. Tamblin. 1987. "Delamination Behaviour of Carbon Fibre/PEEK Composites," Toughened Composites, ASTM STP 937, p. 358.

10.

Davies, P. and F.X. deCharentenay . 1987. "The Effect of Temperature on the Interlaminar Fracture of Tough Composites," ICCM VI , 3:3.284.

11.

Hashemi, S. , A.J. Kinloch and J.G. Williams. 1989. "Corrections Needed in Double-Cantilever Beam Tests for Assessing the Interlaminar Failure of Fibre-Composites." J. Materials Sci. Letters, 8:125.

12.

Hashemi, S. , A.J. Kinloch and J.G. Williams. 1990. "The Analysis of Interlaminar Fracture in Uniaxial Fibre-Polymer Composites," Proc. Royal Soc., A427:173.

13.

Hashemi, S. , A.J. Kinloch and J.G. Williams. 1990. "Mechanics and Mechanisms of Delamination in a PES-Fibre Composite," Composites Sci. Tech., 37:429.

14.

Williams, J.G. 1989. "End Corrections for Orthotropic DCB Specimens." Composites Sci. Tech., 35:367.

15.

Kinloch, A.J. and R.J. Young. 1983. The Fracture Behaviour of Polymers, New York: Applied Science , p. 300.

16.

Kinloch, A.J. and J.G. Williams. 1980. "Crack Blunting Mechanisms in Polymers," J. Materials Sci., 15:987.

17.

Russell, A.J. and K.N. Street. 1987. "The Effect of Matrix Toughness on Delamination," Toughened Composites , ASTM STP 937, p. 275.

18.

Chai, H. 1986. "On the Correlation between the Mode I Failure of Adhesive Joints and Laminated Composites," Engng. Fracture Mechs., 24:413.

19.

Ilcewicz, L.B. , P.E. Keary and J. Trostle. 1988. " Interlaminar Fracture Toughness Testing of Composite Mode I and Mode II Specimens," Polymer Engng . Sci., 28:592.

20.

Williams, J.G. 1988. "On the Calculation of Energy Release Rates for Cracked Laminates," Intern. J. Fracture , 36: 101.

21.

Bascom, W.D. , R.L. Jones and C.O. Timmons. 1975. In Adhesion Science and Technology, L. H. Lee , ed. New York: Plenum Press, 9B:501.

22.

Williams, J.G. 1989. "Fracture Mechanics of Delamination Tests," J. Strain Analysis, 24:207.

23.

Rothschilds, R.J. , J.W. Gillespie and L.A. Carlsson. 1988. " Instability-Related Delamination Growth in Thermoset and Thermoplastic Composites ," Composite Materials, Testing and Design, ASTM STP 972, p. 161.

24.

Johannesson, T. , P. Sjoblom and R. Selden. 1984. " The Detailed Structure of Delamination Fracture Surfaces in Graphite/Epoxy Laminates," J. Materials Sci., 19:1171.

25.

Robertson, R.E. and V.E. Mindroiu. 1985. "The Stacked Lamellar Texture on the Fracture Surfaces of Fibre Composites," J. Materials Sci., 20:2801.

26.

Kinloch, A.J. , D.G. Gilbert and S.J. Shaw. 1986. " A Mechanism for Ductile Crack Growth in Epoxy Polymers," J. Materials Sci., 21:1051.