Simulation of self-heating in unidirectional composite material under fatigue loading observed by infrared thermography
Topic(s) : Material and Structural Behavior - Simulation & Testing
Co-authors :
Yan YAN (FRANCE), Marie-Laetitia PASTOR (FRANCE), Emmanuelle ABISSET CHAVANNE , Xiaojing XIAOJING GONG (FRANCE)Abstract :
Under cyclic fatigue loading, a material can generate heat due to its internal friction and damages occurring during the process, which we call the self-heating phenomenon. With the help of an infrared thermographic camera, the temperature variation on the surface of the material can be obtained. It is shown that this phenomenon has a strong correlation with damage accumulation in material during the fatigue process, so it can be explored to study the fatigue behavior of materials. This method, proposed initially for metals, has been also applied to composite laminates with success. It allows us to evaluate the fatigue progress to predict quickly the fatigue limit and the S-N curve for a given composite in only one day.
However, the physical principles of the self-heating phenomenon in a composite structure are not thoroughly understood, since the composite is heterogeneous and anisotropic where the damage mechanisms are complicated. To give a convincing explanation, a thermomechanical model should be built to simulate the mechanical and thermal behaviors during fatigue. This is a complex process considering the interaction between mechanical and thermal responses, and the anisotropic property of composite material.
Recall that in the literature, a numerical thermomechanical fatigue model for a composite is usually based on the results from traditional fatigue tests, which is time-consuming and may take months. Using fatigue tests associated with infrared thermography, necessary parameters for the building of the thermomechanical model, especially the stiffness degradation law, can be obtained quickly, which greatly shortens the model preparation period. However, this method still needs to be compared with the traditional fatigue test method to verify its feasibility and reliability.
In this work, a thermomechanical model was proposed to simulate the mechanical and thermal fatigue behavior of composite material under cyclic fatigue loading. This model was composed of two parts: a mechanical part to simulate the mechanical behavior and continuous damage during fatigue process, and a thermal part to simulate the heat generation and dissipation. The viscoelasticity and plasticity of the polymer matrix and the damages of the composite were considered as heat generation, and a portion of this generated heat was dissipated through conduction and convection. To prove the efficiency of determining the stiffness degradation law of material by infrared thermography, the degradation law obtained by traditional method was also implemented separately in the thermomechanical model. The simulation results of the two methods were analyzed and compared with each other to verify the possibility of obtaining the stiffness degradation law from fatigue tests associated with infrared thermography. The simulation results of self-heating temperature were also compared with experimental data to explain the principles of heat generation during the fatigue process.
However, the physical principles of the self-heating phenomenon in a composite structure are not thoroughly understood, since the composite is heterogeneous and anisotropic where the damage mechanisms are complicated. To give a convincing explanation, a thermomechanical model should be built to simulate the mechanical and thermal behaviors during fatigue. This is a complex process considering the interaction between mechanical and thermal responses, and the anisotropic property of composite material.
Recall that in the literature, a numerical thermomechanical fatigue model for a composite is usually based on the results from traditional fatigue tests, which is time-consuming and may take months. Using fatigue tests associated with infrared thermography, necessary parameters for the building of the thermomechanical model, especially the stiffness degradation law, can be obtained quickly, which greatly shortens the model preparation period. However, this method still needs to be compared with the traditional fatigue test method to verify its feasibility and reliability.
In this work, a thermomechanical model was proposed to simulate the mechanical and thermal fatigue behavior of composite material under cyclic fatigue loading. This model was composed of two parts: a mechanical part to simulate the mechanical behavior and continuous damage during fatigue process, and a thermal part to simulate the heat generation and dissipation. The viscoelasticity and plasticity of the polymer matrix and the damages of the composite were considered as heat generation, and a portion of this generated heat was dissipated through conduction and convection. To prove the efficiency of determining the stiffness degradation law of material by infrared thermography, the degradation law obtained by traditional method was also implemented separately in the thermomechanical model. The simulation results of the two methods were analyzed and compared with each other to verify the possibility of obtaining the stiffness degradation law from fatigue tests associated with infrared thermography. The simulation results of self-heating temperature were also compared with experimental data to explain the principles of heat generation during the fatigue process.