Material damping characteristics of 2-D and 3-D textile structural composites were investigated. A model for predicting damping in these materials was developed based upon the classical laminated plate theory. The model entailed 18 material constants and made use of the Kirchoff-Love hypothesis, the elastic-viscoelastic correspondence principle, and some existing models for predicting the static moduli of textile structural composites. These 18 constants included 6 for describing the stretching stiffness matrix represented by [A], another 6 for the bendingstretching coupling stiffness matrix represented by [B], and the other 6 for the bending stiffness matrix represented by [D]. To evaluate the theoretical values of damping, the storage stiffness elements of [A], [B] and [D] were determined by first expressing [A], [B], and [D] in terms of the stiffness matrix [Q]k. and layer thickness hk, of each lamina. The components of Qijk were in turn expressed in terms of the 4 basic engineering constants EL, ET, GLT and υLT. The basic engineering constants were replaced by their corresponding complex moduli by making use of the elastic and viscoelastic correspondence principle: e.g., stretching damping, Aηij= A'ij/A'ij; coupling damping, Bηij= B'ij/B'ij; and bending damping, Dηij= D'ij/D'ij. In this study, the basic damping loss factors ηL， ηT, ηLT, ηυLT were determined by a modified Hashin's theory and Rule-of-Mixture Laws. From numerical results, we concluded that stretching damping, stretching-bending damping, bending damping and engineering damping coefficients are al1 functions of ng (a geometric parameter) in 2-D woven textile structural composites. Also, the axial damping, the in-plane shear damping and the in-plane Poisson's damping coefficients are all functions of yarn orientation angle and fiber volume fraction in 3-D braided textile structural composites. Experimental data supported theoretically predicted results.

Material damping characteristics of 2-D and 3-D textile structural composites were investigated. A model for predicting damping in these materials was developed based upon the classical laminated plate theory. The model entailed 18 material constants and made use of the Kirchoff-Love hypothesis, the elastic-viscoelastic correspondence principle, and some existing models for predicting the static moduli of textile structural composites. These 18 constants included 6 for describing the stretching stiffness matrix represented by [A], another 6 for the bendingstretching coupling stiffness matrix represented by [B], and the other 6 for the bending stiffness matrix represented by [D]. To evaluate the theoretical values of damping, the storage stiffness elements of [A], [B] and [D] were determined by first expressing [A], [B], and [D] in terms of the stiffness matrix [Q]k. and layer thickness hk, of each lamina. The components of Qijk were in turn expressed in terms of the 4 basic engineering constants EL, ET, GLT and υLT. The basic engineering constants were replaced by their corresponding complex moduli by making use of the elastic and viscoelastic correspondence principle: e.g., stretching damping, Aηij= A'ij/A'ij; coupling damping, Bηij= B'ij/B'ij; and bending damping, Dηij= D'ij/D'ij. In this study, the basic damping loss factors ηL， ηT, ηLT, ηυLT were determined by a modified Hashin's theory and Rule-of-Mixture Laws. From numerical results, we concluded that stretching damping, stretching-bending damping, bending damping and engineering damping coefficients are al1 functions of ng (a geometric parameter) in 2-D woven textile structural composites. Also, the axial damping, the in-plane shear damping and the in-plane Poisson's damping coefficients are all functions of yarn orientation angle and fiber volume fraction in 3-D braided textile structural composites. Experimental data supported theoretically predicted results.

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