STIFFNESS CHARACTERISTICS OF TWISTED CORDS FOR CORD RUBBER COMPOSITES

A finite element model is presented to predict the stiffness character istics of twisted cords by treating them as structures and considering the stiffness couplings due to extension-bending-torsional deformatio ns. The axial, bending, and torsional stiffnesses are calculated for b oth the aramid-cord and steel-cord, and compared to an approximate exp ression with good agreement where applicable. To illustrate the stiffn ess behavior, all the three stiffnesses are presented with variations in the number of twists per unit length, the surrounding rubber modulu s and the thickness. The stiffness couplings among the extension, bend ing, and twisting deformations are presented for aramid-cords with var ying number of twists per unit length and rubber thickness. The result s illustrate that stiffness characteristics are strongly dependent upo n the number of twists per unit length, type of cord, surrounding rubb er layer thickness and modulus. The stiffness couplings presented illu strate the mechanisms of load transfer, which are important for unders tanding failure mechanisms of cords, and cord-rubber composites.