The translaminate fracture behavior of carbon/epoxy structural laminates with through-penetration notches was investigated to develop a residual strength prediction methodology for composite structures. An experimental characterization of several composite materials systems revealed a fracture resistance behavior that resembles the R-curve behavior exhibited by ductile metals. Fractographic examinations led to the postulate that the damage growth resistance was primarily due to fractured fibers in the principal load-carrying plies being bridged by intact fibers of the adjacent plies. The load transfer associated with this bridging mechanism suggests that a progressive damage analysis methodology will be appropriate for predicting the residual strength of laminates with through-penetration notches. A progressive damage methodology developed by the authors was used to predict the initiation and growth of matrix cracks and fiber fracture. The residual strength predictions for different panel widths, notch lengths, and material systems were in reasonable agreement to the experimental failure loads.
1. Poe, C. C., Jr., "A Unifying Strain Criterion for Fracture of Fibrous Composite Laminates,"Engineering Fracture Mechanics, Vol. 17, No. 2, pp. 153-171, 1983.
2.
2. Harris, C. E. and D. H. Morris, "A Fractographic Investigation of the Influence of Stacking Sequence on the Strength of Notched Laminated Composites,"Fractography of Modern Engineering Materials: Composites and Metals, ASTM STP 948, J. E. Masters and J. J. Au, Eds., American Society for Testing and Materials, Philadelphia, 1987, pp. 131-153.
3.
3. Harris, C. E. and D. H. Morris, "On the Use of Crack-Tip-Opening Displacement to Predict the Fracture Strength of Notched Graphite/Epoxy Laminates,"Experimental Mechanics, Vol. 25, No. 2, June 1985.
4.
4. Poe, C. C., Jr., C. E. Harris, and D. H. Morris. "Surface Crack Analysis Applied to Impact Damage in a Thick Graphite/Epoxy Composite,"Surface-Crack Growth: Models, Experiments, and Structures, ASTMSTP 1060, W. G. Reuter, J. H. Underwood and J. C. Newman, Jr., Eds., American Society for Testing and Materials, Philadelphia, 1990, pp. 194-212.
5.
5. Poe, C. C., Jr., C. E. Harris,T. W. Coats, and T. H. Walker. "Tension Strength with Discrete Source Damage,"Proceedings of the Fifth NASA/DOD Advanced Composites Technology Conference, CP 3294, Vol. I, Part I, Seattle, Washington, Aug. 1994, pp. 369-438.
6.
6. Chamis, C. C., P. L. N. Murthy, and L. Minnetyan. "Structural Behavior of Composites with Progressive Fracture,"J. ofReinforced Plastics and Composites, Vol. 11, April 1992, pp.413-442.
7.
7. Talreja, R."A Continuum Mechanics Characterization of Damage in Composite Materials,"Proc. R. Soc. London, Vol. 399A, 1985, pp. 126-216.
8.
8. Talreja, R."Residual Stiffness Properties of Cracked Composite Laminate,"Advanced in Fracture Research, Proc. Sixth Int. Conf De Fracture, New Delhi, India, Vol.4,1985, pp.3013-3019.
9.
9. Ladeveze, P."A Damage Computational Method for Composite Structures,"Computers and Structures, Vol. 44, No. 1/2, 1992, pp. 79-87.
10.
10. Chang, K-Y, L. Sheng, and F-K Chang. "Damage Tolerance of Laminated Composites Containing an Open Hole and Subjected to Tensile Loadings,"J. of Composite Materials, Vol. 25, March 1991, pp. 274-301.
11.
11. Chang, F-K and K-Y Chang. "A Progressive Damage Model for Laminated Composites Containing Stress Concentrations,"J. of Composite Materials, Vol. 21, Sept. 1987, pp. 834-855.
12.
12. Allen, D. H., S. E. Groves, and C. E. Harris. "A Cumulative Damage Model for Continuous Fiber Composite Laminates with Matrix Cracking and Interply Delamination,"Composite Materials: Testing and Design (8th Conference), ASTM STP 972, J. D. Whitcomb, Ed., American Society for Testing and Materials, Philadelphia, 1988, pp. 57-80.
13.
13. Lee, J. W., D. H. Allen, and C. E. Harris. "Internal State Variable Approach for Predicting Stiffness Reductions in Fibrous Laminated Composites with Matrix Cracks,"J. of Composite Materials, Vol. 23, Dec. 1989, pp. 1273-1291.
14.
14. Harris, C. E. and D. H. Allen. "A Continuum Damage Model of Fatigue-Induced Damage in Laminated Composites,"SAMPE Journal, July/August 1988, pp. 43-51.
15.
15. Lo, D. C., D. H. Allen, and C. E. Harris. "A Continuum Model for Damage Evolution in Laminated Composites,"Inelastic Deformation of Composite Materials, G. J. Dvorak, ed., Springer-Verlag, 1990, pp. 549-561.
16.
16. Coats, T. W. and C. E. Harris. "Experimental Verification of a Progressive Damage Model for IM7/5260 Laminates Subjected to Tension-Tension Fatigue,"J. of Composite Materials, Vol. 29, No. 3, 1995, pp. 280-305.
17.
17. Lo, D. C., T. W. Coats, C. E. Harris and D. H. Allen. "Progressive Damage Analysis of Laminated Composite (PDALC) (A Computational Model Implemented in the NASA COMET Finite Element Code),"National Aeronautics and Space Administration Technical Memorandum 4724, August 1996.
18.
18. Lagace, P. A., N. V. Bhat and A. Gundogdu. "Response of Notched Graphite/Epoxy and Graphite/ Peek Systems,"Composite Materials: Fatigue and Fracture, Fourth Volume, ASTM STP 1156, W. W. Stinchcomb and N. E. Ashbaugh, Eds., American Society for Testing and Materials, Philadelphia, 1993, pp. 55-71.
19.
19. Scholz, D. B., E. F. Dost and B. W. Flynn. "Advanced Technology Composite Fuselage-Materials and Processes," National Aeronautics and Space Administration Contractor Report 4731, 1995.
20.
20. Coquill, S. L. and D. F. Adams. "Mechanical Properties of Several Neat Polymer Matrix Materials and Unidirectional Carbon Fiber-Reinforced Composites," National Aeronautics and Space Administration Contractor Report 181805, April 1989.
21.
21. Dawicke, D. S., J. C. Newman, Jr., M. A. Sutton and B. E. Amstuz. "Influence of Crack History on the Stable Tearing Behavior of a Thin-sheet Material with Multiple Cracks,"FAA/NASA International Symposium onAdvanced Structural IntegrityMethods ofAirframe Durability and Damage Tolerance, NASA CP 3274, Charles E. Harris, editor, National Aeronautics and Space Administration, Washington, D.S., September 1994, pp. 193-212.
22.
22. deWit, R., R. J. Fields, L. Mordfin, S. R. Low and D. Harne, "Fracture Behavior of Large-Scale Thin-Sheet Aluminum Alloy,"FAA/NASA International Symposium on Advanced Structural Integrity MethodsforAirfram Durability and Damage Tolerance, NASA CP 3274, Charles E. Harris, editor, National Aeronautics and Space Administration, Washington, D.C., pp. 963-984.
23.
23. Buie, K. D. "A Finite Element Model for Laminated Composite Plates with Matrix Cracks and Delaminations," Thesis, Texas A&M University, December, 1988.
24.
24. Jones, Robert M.Mechanics of Composite Materials, Hemisphere Publishing Corporation, 1975.
25.
25. Whitney, J. M. and R. J. Nuismer. "Stress Fracture Criteria for Laminated Composites Containing Stress Concentrations,"J. Composite Materials, Vol. 8, pp. 253-265, 1974.
26.
26. Nuismer, R. J. and J. M. Whitney. "Uniaxial Failure of Composite Laminates Containing Stress Concentrations,"Fracture Mechanics of Composites, ASTM STP 593, American Society of Testing and Materials, pp. 117-142, 1975.
27.
27. Tada, H., P. C. Paris and G. R. Irwin. The Stress Analysis of Cracks Handbook, Del Research Corp., St. Louis, MO, 1973.
