Accession Number : AD0808786

Title :   ON DYNAMIC THEORIES OF FIBER-REINFORCED COMPOSITES.

Descriptive Note : Technical rept.,

Corporate Author : NORTHWESTERN UNIV EVANSTON IL STRUCTURAL MECHANICS LAB

Personal Author(s) : Herrmann, George ; Achenbach, Jan D.

Report Date : JAN 1967

Pagination or Media Count : 10

Abstract : The well-known effective modulus theory of fiber-reinforced composites is generally suitable for static analysis. For dynamic problems, however, its applicability is less certain. The dispersion of free harmonic waves, for example, to be expected in an extended composite, cannot be accounted for by the effective modulus theory. In this paper a theory is proposed for the dynamic analysis of layered and fiber-reinforced composites, in which the identity of reinforcing elements is preserved. The elastic and geometric properties of the sheets or fibers are combined into effective stiffnesses. With the aid of certain supplementary kinematical assumptions describing the deformations of the reinforcing elements a single set of field equations is derived. The equations of motion presented are analogous to those of the theory of linear elasticity with microstructure. To test the viability of the proposed theory the dispersion characteristics of free harmonic waves propagating in the direction of the reinforcing elements are analyzed. For a periodic structure consisting of alternating layers the 'exact' dispersion curves for the lowest mode were obtained by solving the appropriate elasticity problem. The approximate and exact dispersion curves are compared. (Author)

Descriptors :   *DYNAMICS), *REINFORCING MATERIALS), (*COMPOSITE MATERIALS, (*FIBERS, (*LAMINATES, ELASTIC PROPERTIES), THEORY, MATHEMATICAL ANALYSIS, THICKNESS.

Subject Categories : Laminates and Composite Materials
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE