Cooling Transient Thermal Stress In Composite Gradient EFBC And EFBF Board With Temperature-dependent Material Properties

In order to research the thermal stress distribution and controlling factors of thecooling transient thermal stress in composite gradient EFBC and EFBF board withtemperature-dependent material properties which under the cooling boundary condition,according to the three laws of thermodynamics and the material constitutive relation，westarted from the equation of heat conduction and the corresponding functional．Adopting variational finite element method in the space domain and finite differencemethod in the time domain and appling a linear interpolation function to describe thetemperature field mode，finally，we established the finite element basic equation of theFGM composite panel．On this basis，according to the thermo-elastic theory，we get thebasic equations of the thermal stress field by using integration methods of simpsonnumerical for the complex integration．According to the basic equations of heat conduction and thermal stress，wecompiled the corresponding calculation program by the use of high-level language ofFORTRAN77computer．Comparing with the result of degeneration with the researchquestion and literature results， we verified the correctness of the researchmethods．Adopting the mesomechanics model for the material properties of gradientlayer，we acquired the regularities of distribution of Transient thermal stress aboutComposite FGM board which comprised by Ti-6Al-4V/ZrO₂on the base of numericalcomputation and analysis．We researched the influence of kinds of factors，such astemperature-indepengent properties，porosities A，component distribution shape actor Mand the gradient layer．The main analysis results are as follows：（1） The effect of the thickness of gradient layer of EFBC and EFBF compositepanels：With the decrease of the thickness of the gradient layer，the temperature curvechanges to easing；（2） The effect of the porosity of gradient layer of EFBC and EFBF compositepanels：With the increase of the porosity of the FGM layer，the uneven of thematerial distribution increase．The smaller the porosity is，the smaller the change of thethermal stress curve of composite panels is；（3） When the composition distribution of the material shape factor M<1，the heatstress curve of the composite plate generated mutation，when the M=1，the heat stress curve is smooth and no mutation．Besides，when the M>1，With time goes on，thethermal stress curve of composite boards increased．In summary，when the M=1，thethermal stress curve was ideal；（4） Under the same conditions of porosity A，component M and plate thickness，EFBC composite panels which were variable physical property having a more gentlethermal stres curve，no mutation and low peak than the composite panels which wereconstant physical property，The status of EFBC composite panels was composite．The results of this paper provide a reference for the further application ofheat-resistant protective materials in thermal stress and aerospace engineering．...