Stiffness characteristics of twisted cords for cord-rubber composites

Abstract

A finite element model is presented to predict the stiffness characteristics of twisted cords by treating them as structures and considering the stiffness couplings due to extension-bending-torsional deformations. The axial, bending, and torsional stiffnesses are calculated for both the aramid-cord and steel-cord, and compared to an approximate expression with good agreement where applicable. To illustrate the stiffness behavior, all the three stiffnesses are presented with variations in the number of twists per unit length, the surrounding rubber modulus and the thickness. The stiffness couplings among the extension, bending, and twisting deformations are presented for aramid-cords with varying number of twists per unit length and rubber thickness. The results illustrate that stiffness characteristics are strongly dependent upon the number of twists per unit length, type of cord, surrounding rubber layer thickness and modulus. The stiffness coupling presented illustrate the mechanisms of load transfer, which are important for understanding failure mechanisms of cords, and cord-rubber composites.