Theoretic and Experimental Fatigue Analysis of Off-axis Unidirectional Rubbery Composites Using Nonlinear Life Prediction Model

The aim of this article is analyzing the fatigue behavior of off-axis unidirectional rubbery composites under uniaxial tension-tension cyclic loading based on developed damage-entropy model. The main advantage of the damage-entropy model is that it accounts the viscoelastic property and temperature increase during the fatigue loading conditions. The off-axis rubbery composites lay-ups exhibit a nonlinear stress-strain response similar to the rubber matrix. Hence, the Newton-Raphson method is employed to capture the nonlinear behavior of rubbery composites. The failure criterion in the damage-entropy model is based on the fracture fatigue entropy value. To characterize the longitudinal, transverse, and in-plane shear behavior of rubbery composites, static and fatigue experimental tests on [0]2, [90]4, and [±45]s are conducted. Moreover, the damage energy, the energy dissipation due to viscoelastic behavior and the heat transfer to the environment during the fatigue loading will be calculated. Furthermore, the experimental results of [45]4 lay-up are utilized to validate the developed damage-entropy model. Finally, the experimental and modeling results of hysteresis energy, temperature change, and fatigue life of SCRC [45]4 lay-up for different stress levels subjected to stress ratio 0.1 and 1 Hz frequency, are compared. The comparison between the analytical results and experiments indicates the capabilities of the present model.