Analysis Of Moisture And Heat Effects Of Composite Laminates At Microscopic Scale

When the size of the material is at the level of micro and nano,the influence of some defects or inclusions in the internal space of the material on the material performance begins to show,leading to the non-uniformity of the material property and producing the phenomenon of scale effect.In the traditional continuum theory,because the material scale parameters are not taken into account,it is no longer applicable at the micro-nano level.This paper mainly uses the theory of even stress to analyze the phenomenon of scale effect.Because the classical theory of even stress contains too many material scale parameters,it is difficult to calculate,which limits its application in practical engineering.Although the modified even stress theory contains only one material scale parameter,it is only applicable to isotropic materials and cannot be used in the scale effect analysis of anisotropic materials.In view of this,based on the newly modified even stress theory,this paper deduces the equilibrium equation through the virtual work principle,and establishes the wet and thermal stability model of Mindlin laminates under the joint action of mechanical load and wet and hot load.The critical buckling loads of laminated plates under different environmental conditions are calculated and the scale effect is analyzed.The specific work is as follows:1.The scale effect of critical buckling loads on laminated plates under different environmental conditions is analyzed by using the established model of moisture and heat stability.The results show that the critical buckling load of the laminates increases with the increase of the material scale parameters,and is larger than the critical buckling load under the classical theory,which proves the existence of the scale effect.The single change and combined action of temperature and humidity have influence on the critical buckling load,and the influence of temperature on the critical buckling load is greater than that of humidity.2.To meet C0 continuity conditions of the coordination unit BCIZ nine parameters and satisfy the weak C1 continuity conditions of fixed nine parameter triangular thin plate bending element RT9 as the foundation,using the finite element method to calculate the mesoscopic scale of plate buckling critical load under hot and humid environment,the results show that the finite element method to the different conditions of plate buckling critical load is calculated,and the ability to analyze the scale effect.