The elastic properties of graphite/epoxy composites with three-dimensional interlock weave reinforcement have been measured over length scales somewhat greater than the characteristic length of the weave pattern. Orientation averaging models similar to those developed elsewhere over the last twenty years provide estimates of elastic constants that are in fair agreement with the experimental data. However, in-plane Young's moduli are consistently too high and properties related to the through-thickness reinforcement show considerable scatter. Most of the discrepancies can be attributed to waviness and other geometrical irregularities in nominally straight tow segments. Much improved agreement with in-plane properties is obtained by measuring and accounting for the out-of-plane waviness of in-plane tows. Other observed distortions of in-plane tows and irregularity in through-thickness tows are very difficult to quantify experimentally. There results a significant and apparently unavoidable uncertainty in predictions of properties that depend strongly on the through-thickness reinforcement. Nevertheless, the utility of orientation averaging models in applications where the in-plane properties are paramount is clearly verified.
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References
1.
1. Bradshaw, F. J., G. Dorey and G. R. Sidey. 1973. "Impact Resistance of Carbon Fiber Reinforced Plastics," Tech. Rep. 72240, Royal Aircraft Establishment, England.
2.
2. Novak, R. C.1975. "Materials Variables Affecting the Impact Resistance of Graphite and Boron Composites-II," Rep. TR-74-196, Part Il, U.S. Air Force Materials Laboratory, Dayton, OH.
3.
3. McAllister, L. E. and W. L. Lachman. 1983. In Fabrication of Composites, Handbook of Composites, Vol. 4. New York: Elsevier, p. 109.
4.
4. Guess, T. R. and E. D. Reedy, Jr.1985. J. Comp. Tech. Res., 7:136.
5.
5. Reedy, E. D., Jr. and T. R. Guess. 1986. J. Comp. Tech. Res., 8:163.
6.
6. Mignery, L. A., T. M. Tan and C. T. Sun. 1985. In Delamination and Debonding, ASTM Spec. Tech. Publ. 876, W. S. Johnson, ed., Philadelphia, PA: ASTM, pp. 371-385.
7.
7. Smith, P. J. and R. D. Wilson. 1985. "Damage Tolerant Composite Wing Panels for Transport Aircraft," NASA Contractor Report 3951, Boeing Commercial Airplane Company.
8.
8. Chou, T.-W., R. L. McCullough and R. B. Pipes. 1986. "Composites,"Scientific American, 254(10):193-203.
9.
9. Ko, F.1989. In Textile Structural Composites; Composite Materials, 3, T.-W. Chou and F. Ko, eds., New York: Elsevier, Chapter 5.
10.
10. Horton, R. E. and J. E. McCarty. 1987. In Engineered Materials Handbook, Vol. 1, Composites, C. A. Dostal, ed., Metals Park, OH: Am. Soc. Metals.
11.
11. Brandt, J., K. Dreschler and R. Meistring. 1990. "The Application of Three-Dimensional Fiber Preforms for Aerospace Composites,"Prac. ESA Symp. on Space Applications of Advanced Structural Materials, ESTEC, Noordwijk, Netherlands, March (ESA SP-303, June, 1990), pp. 71-77.
12.
12. Cox, B. N., M. S. Dadkhah, R. V. Inman, W. L. Morris and J. Zupon. 1992. "Mechanisms of Compressive Failure in 3D Composites,"Acta Metall. Mater., 40:3285-3298.
13.
13. Cox, B. N., M. S. Dadkhah, W. L. Morris and J. G. Flintoff. 1994. "Failure Mechanisms of 3D Woven Composites in Tension, Compression, and Bending,"Acta Metall. Mater., 42:3967-3984.
14.
14. Cox, B. N., M. S. Dadkhah and W. L. Morris. "On the Tensile Failure of 3D Woven Composites," submitted to Composites.
15.
15. Dadkhah, M. S., B. N. Cox and W. L. Morris. "Compression-Compression Fatigue of 3D Woven Composites,"Acta Metall. Mater., in press.
16.
16. Tarnopol'skii, Y. M., V. A. Polyakor and I. G. Zhigun. 1973. "Composite Materials Reinforced with a System of Three Straight, Mutually Orthogonal Fibers, I: Calculation of Elastic Characteristics,"Polymer Mechanics, 5:853-860.
17.
17. Kregers, A. F. and Y. G. Melbardis. 1978"Determination of the Deformability of Three-Dimensional Reinforced Composites by the Stiffness Averaging Method,"Polymer Mechanics, 1:3-8.
18.
18. Kregers, A. F. and G. A. Teters. 1981. "Determination of the Elasto-Plastic Properties of Spatially Reinforced Composites by the Averaging Method,"Mech. Comp. Mater., 17:25-31.
19.
19. Yang, J.-M., C.-L. Ma and T.-W. Chou. 1986. "Fiber Inclination Model of Three-Dimensional Textile Structural Composites,"J. Composite Materials, 20:472-484.
20.
20. Gowayed, Y. A. and C. M. Pastore. 1991. "Analytical Techniques for Textile Structural Composites: A Comparative Study of US-USSR Research,"Fber-Tex 90, Clemson, SC, August 1990, NASA Conf. Publ. 3128, J. D. Buckley, ed., NASA.
21.
21. Cox, B. N., W. C. Carter and N. A. Fleck. 1994. "A Binary Model of Textile Composites. I Formulation,"Acta Metall. Mater., 42:3463-3479.
22.
22. Xu, J., B. N. Cox, M. A. McGlockton and W. C. Carter. "A Binary Model of Textile Composites: II The Elastic Regime," to Acta Metall. Mater., in press.
23.
23. Cox, B. N., M. S. Dadkhah, R. V. Inman, J. Flintoff, M. R. Mitchell and W. L. Morris. 1993. "Design and Reliability Guide for Triaxially Braided Composites,"Rockwell International Science Center, Report to Rockwell Plastic Products Division, November.
24.
24. Cox, B. N., M. S. Dadkhah, M. R. Mitchell and T. W. Kniveton. "The Effects of Tow Waviness on the Stiffness, Strength, and Fatigue Life of Triaxially Braided Composites," to be submitted to J. Comp. Mater.
25.
25. Wilks, S. S.1962. Mathematical Statistics. New York: John Wiley and Sons.
27. Ifju, P. G. Univ. Florida, private communication.
28.
28. Hashin, Z.1979. "Analysis of Properties of Fiber Composites with Anisotropic Constituents,"J. Appl. Mech., 46:543-550.
29.
29. Hill, R.1965. "Theory of Mechanical Properties of Fiber-Strengthened Materials-III. Self-Consistent Model,"J. Mech. Phys. Solids, 13:189-198.
30.
30. Christensen, R. M.1990. "A Critical Evaluation for a Class of Micromechanics Models,"J. Mech. Phys. Solids, 38:379-404.
31.
31. Naik, R. 1992. NASA Technical Memorandum.
32.
32. Love, A. E. H.1944. A Treatise on the Mathematical Theory of Elasticity. New York: Dover, Articles 12 and 49.
33.
33. Lee, J.-W. and C. E. Harris. 1990. "A Deformation-Formulated Micromechanics Model of the Effective Young's Modulus and Strength of Laminated Composites Containing Local Ply Curvature," ASTM STP 1059, S. P. Garbo, ed., Philadelphia: ASTM, pp. 521-563.
34.
34. Van Fo Fy, G. A.1966. Polymer Mechahics, 2:593-602.
