چكيده به لاتين
As the strength and stiffness of composite materials under cyclic loading decreases sharply, the fatigue properties of composites become more important because they have a significant effect on the safety of parts and structures. Conventional methods for obtaining and estimating properties require long time and many samples. In recent years, many activities have been done to predict the fatigue properties and behavior of composite materials in a shorter period of time. One of these methods is the thermographic method, which predicts the fatigue behavior based on the temperature and heat generated in the sample by performing a fatigue test. In general, if we want to classify the heat generated in the fatigue test, it is divided into two parts: heat generated due to internal wear and irreversible changes (crack growth, layer separation, etc.). It should also be noted that most fatigue damage is caused by irreversible changes and internal wear does not have much effect on the damage. Research shows that the amount of total heat generated by failure is almost independent of the applied stress level. Based on this behavior, a rapid method for predicting the S-N diagram in a short time is expressed by measuring the temperature rise diagrams under cyclic loading and guiding one or two pieces to the final failure. Some properties of fatigue can be investigated through temperature development diagrams. These properties studied in this study include: fatigue limit, fatigue life, estimation of heat generated in the form of numerical simulations and theoretical relations, study of the relationship between stress ratio and temperature changes, estimation of sample strength. Fatigue limit for the sample of this study is estimated from two methods of thermography and mechanical energy loss.
