38—THE STRESS–STRAIN PROPERTIES OF MULTI-PLY CORDS PART I. THEORY

The energy method, previously used for the derivation of the stress–strain properties of continuous-filament yarns (Treloar and Riding, J. Text. Inst., 1963, 54, T156), is applied to the derivation of the corresponding properties of continuous-filament cords of 2-ply, 3-ply and 7-ply construction. The calculations make use of the author's theory of the cord geometry (Treloar, J. Text. Inst., 1956, 47, T348) whereby the torsion in the ply may be obtained from the twist in the original single yam and the geometrical parameters of the cord. The material properties are introduced in the form of the stress–strain curve of the filament material, as obtained experimentally. Equations are derived for the stress–strain properties of the cord in terms of experimentally observable parameters; these are presented in a form suitable for numerical computation.