The Effect of void and Fiber Variations on the Accuracy of Composite Material Characterizations

Abstract

A concise matrix formulation is presented to illustrate the effects of experimental uncertainties on the characterization of anisotropic com posite materials. The matrix equations permit a graphic illustration of the individual roles played by measurement errors, sample variations, and the degree of anisotropy on the computation of the anisotropic stiffness co efficients. With particular reference to the characterization of materials containing voids, it is shown that variations in the void content can lead to material constants which appear to violate the symmetry conditions assumed for hyperelastic materials. A simple statistical test is recom mended for the evaluation of characterization experiments whenever the contribution of error is uncertain.

Get full access to this article

View all access options for this article.

References

J.C. Swearengen and T.R. Guess , "Mechanical Behavior of Metal-Metal Composite Cylinders," Conference Proceedings, Failure Modes in Composites, American Society for Metals, in press.

C.W. Bert and T.R. Guess , "Mechanical Behavior of Carbon/Carbon Filamentary Composites," Second Conference, Composite Materials: Testing and Design, ASTM STP 497, 1972, p. 89.

W. Oettli , W. Prager , and J.H. Wilkinson , "Admissible Solutions of Linear Systems with not Sharply Defined Coefficients ," J. SIAM, Numerical Analysis, Ser. B, Vol. 2 (1965), p. 291.

J.E. Ashton , J.C. Halpin , and P.H. Petit , Primer on Composite Materials Technomic Publishing Co., Inc., Westport, CT, (1969).

J.C. Halpin and S.W. Tsai , "Environmental Factors in Composite Material Design," AFML TR 67-423.

K.T. Kavanagh , "Experiment Vs. Analysis: Computational Techniques for the Characterization of Static Material Response," Int. J. Numerical Methods in Engineering, Vol. 5, (1973).

I. Guttman , S.S. Wilks , and J.S. Hunter , Introductory Engineering Statistics, John Wiley and Sons , (1971).