The effect of various factors on delamination has been studied using uni directional glass fibre and carbon fibre-epoxy specimens with cut central plies. It is con cluded that the fracture energy is not a material constant. Among the various factors which affect the fracture energy, the specimen thickness and the through thickness normal stress are the two most significant ones. A simple model is proposed to take account of these two factors. The new model gives excellent correlation with experimental results and is able to account for the effect of through thickness compressive stresses in mode II fracture, which is ignored in conventional fracture mechanics calculations.
Get full access to this article
View all access options for this article.
References
1.
Rybicki, E.F. , D.W. Schumueser and J. Fox.1977. "An Energy Release Rate Approach for Stable Crack Growth in the Free-Edge Delamination Problem," J. Comp. Mat. , 11:470-487.
2.
O'Brien, T.K.1982. "Characterization of Delamination Onset and Growth in a Composite Laminate," in Damage in Composite Materials, ASTM STP 775, K. L. Reifsnider, ed., American Society for Testing and Materials, pp. 140-167.
3.
Davies, G.A.O. and D.Y. Cui.1989. "Three Dimensional Edge Effects in Composite Plates," Computers and Structures, 31:11-16.
4.
Brewer, J.C. and P.A. Lagace.1988. "Quadratic Stress Criterion for Initiation of Delamination," J. Comp. Mat., 22:1141-1155.
5.
Salpekar, S.A. , I.S. Raju and T.K. O'Brien.1991. "Strain-Energy-Release Rate Analysis of Delamination in a Tapered Laminate Subjected to Tension Load ," J. Composite Materials, 25:118-141.
6.
Williams, J.G.1989. "Fracture Mechanics of Anisotropic Materials," in Application of Fracture Mechanics to Composite Materials, K. Friedrich, ed. , Elsevier Science Publishers, B. V., pp. 3-38.
7.
Prinz, R. and Y. Li.1990. "Interlaminar Mode II Energy Release Rate for Delamination Growth of Graphite/Epoxy Composites," in Selected Papers in Scientific and Technical International Cooperation Program, China Aviation Industry Press, pp. 83-116.
8.
Wisnom, M.R.1991. "Prediction of Delamination in Unidirectional Glass Fibre-Epoxy with Tapered Thickness," Proc. AIAA Structures, Structural Dynamics and Materials Conf, Baltimore, U.S.A., pp. 1162-1172.
9.
Wisnom, M.R.1992. "Prediction of Delamination of Unidirectional Glass Fibre-Epoxy with Dropped Plies," AGARD Conf., CP530 Debonding/Delamination in Composites, Patras, Greece.
10.
Wisnom, M.R.1992. "The Application of Fracture Mechanics to Predict Delamination in Composites," International Symposium on Composite Materials and Structures, Beijing, pp. 370-375.
11.
Wisnom, M.R.1992. "On the Increase in Fracture Energy with Thickness in Delamination of Unidirectional Glass Fibre-Epoxy with Cut Central Plies," J. Reinforced Plastics and Composites, 11:897-909.
12.
Wisnom, M.R. and W. Cui.1992. "Mode II Fracture Energy-A Material Property?," in ECCM Composites Testing and Standardisation , Amsterdam, pp. 433-439.
13.
Cui, W., M.R. Wisnom and M. Jones.1992. "A Comparison of Fracture Criteria to Predict Delamination of Unidirectional Glass/Epoxy Specimens with Cut Central Piles,"in Proceedings of Fibre Reinforced Composites '92, Manchaster, pp. 25/1-25/10.
14.
Prinz, R. and L. Cao.1989. "Analyses of Strain Energy Release Rates for Unidirectional Graphite/Epoxy Laminates with Separated Central Plies Under Fatigue Loading," Proc. 7th International Conference on Composite Materials, Y. Wu, Z. Gu and R. Wu, eds., International Academic Publishers, Vol. 3, pp. 613-618.
15.
Prinz, R. and Gadke, M.1991. "Characterization of Interlaminar Mode I and Mode II Fracture in CFRP Laminates," in Spacecraft Structures and Mechanical Testing, Proc. Int. Conf. Organised by the European Space Agency, ESA SP-321, ESTEC, Noordwijk, The Netherlands, Vol. 1, pp. 97-102.
16.
Haeberle, J. and F.L. Matthews.1990. "Studies on Compressive Failure in Unidirectional CFRP Using an Improved Test Method," Proc. ECCM4 , Stuttgart, pp. 517-523.
17.
ABAQUS, Hibbitt, Karlsson and Sorenson Inc., 100 Medway St., Providence, Rhode Island, 02906, U.S.A.
18.
Bowden, P.B. and J.A. Jukes.1972. "The Plastic Flow of Polymers," J. Mat. Science, 7:52-63.
19.
Cui, W. and M.R. Wisnom.1993. "Effect of Through Thickness Tensile and Compressive Stresses on Fracture Energy," To be published in Journal of Composites Technology and Research.
