An Energy Method For Fatigue Life Predicting Of Composite Materials Under Tensile Load With Different Stress Ratio

The researchers have focused on theoretical and experimental rapid prediction methods of composites materials all the time. Energy theory is one of the most important methods for rapid prediction of fatigue properties. However, there are still many deficiencies in the existing energy dissipation-based fatigue theory especially an integrated study is lacked. To this end, this dissertation aims to establish some valuable method to predict the fatigue life of composites materials in basis of a comprehensive analysis of the fatigue energy process.In order to study the energy change regularity during the fatigue process of composites materials, there are tensile tests and fatigue tests of composites materials conducted with temperature measured by an infrared instrument all the time on glass fiber reinforced composite. Some typical experimental phenomenon and results are analyzed and summarized.The research on hysteresis energy during fatigue process led to the discovery that the transient response of hysteresis energy is related to cycle time and strain amplitude, and the strain amplitude linearly increase with the loading times. On the basis of transient response characters, a calculation model of hysteresis energy is built.From the theory of energy dissipation equilibrium during composites materials fatigue process and analyzing the various forms and mechanics during energy dissipation process, the relations between temperature change, thermal dissipation, plastic deformation energy became apparent. Combined with the material properties of plastic deformation energy and fatigue life, then an energy dissipation model to predict the fatigue life of composites materials is constituted. And from the experimental analysis results, this model has a good accuracy of the life prediction.