Study on viscoelastic properties of cord-rubber composite subjected to biaxial loading

Creep and stress relaxation behaviors of unidirectional nylon6-rubber composite under biaxial tensile loading are studied in this paper. Experiments of creep and stress relaxation are performed at room temperature at different stress levels and different strain levels on both longitudinal and transverse directions respectively. The influence of different stress levels on creep strain and the interaction between longitudinal and transverse stresses are studied. Similar analyses are conducted to assess stress relaxation when specimens are subjected to biaxial tensile loading. These analyses provide solid experimental foundation for understanding nylon6-rubber composite properties. A new relaxation-type constitutive model is presented for predicting stress relaxation behaviors under biaxial tensile condition. In this model, octahedral shear strain is introduced as a variable parameter, which is related to longitudinal strain and transverse strain respectively. Schapery unidirectional integral model and the least square method are applied to determine parameters in the constitutive model. Comparisons of experimental data with theoretical curves are made and good agreements are obtained for rubber composite subjected to biaxial tensile loads.