Meso-scale Mechanical Computing Method On Effective Modulus Of Solid Propellant Based On 2D Voronoi Cell Finite Element Method

Solid propellant is a typical particle-reinforced composite which consists of oxidizing agent particles,incendiary agent particles and binder matrix.The mechanical properties of the solid propellant are closely bound up with the component materials and the meso-structure.So it's of great significance to estimate the mechanical properties of the solid propellant accurately by analyzing the structural integrity and predicting the storage life of grain.Up to now,mesomechanics finite element method is considered as an effective way to study the mechanical properties of the solid propellant.Voronoi Cell Finite Element Method(VCFEM)is used to study the effective modulus of the solid propellant in this dissertation.Many influential factors which describes the solid propellant Representative Volume Element(RVE)effective material properties such as material parameters of the components,packing ratio and the magnitude of load are taken into account.The work is listed as follows:Based on the elastic VCFEM,the finite element format of the solid propellant RVE is established.Based on hybrid stress-element principle,complementary energy function of the VCFEM elements with inclusions is derived from the modified complementary energy function.Then the corresponding element model is obtained.After rigid body displacement being held back and the degrees of freedom being condensed,the finite element governing equation is derived.A VCFEM program cord which is suit for estimating the effective modulus of the solid propellant is set out and the validation of the VCFEM program is verified.The preliminary design of VCFEM program is accomplished through the aspects of the function,the development environment and the composed modules.The VCFEM program cord is set out via the Fortran language characteristics and a 2D elastic VCFEM finite element program which calculates the solid propellant meso-structure effective modulus is compiled.The validation of the VCFEM finite element program is verified by other documents' results and the simulation results.Based on 2D VCFEM and mesomechanics homogenization theory,the effective elastic modulus and the effective Poisson's ratio calculation model of the solid propellant is established.Equalized stress computational formula and equalized strain computational formula are derived via the mesomechanics homogenization theory.Then the effective elastic modulus and the effective Poisson's ratio computational formulas are derived.A 2D model of the solid propellant is built and some analysis over the influential factors such as the value of the load,the propert ies of the matrix,the position of the inclusions and the packing ratio are made.The study shows that: with growing the volume fraction of inclusion,the effective mechanical properties of solid propellant is more and more in common with the inclusion,the effective modulus has accelerated growth and the effective Possion's ratio make some increase.The scale value of the aluminum and AP have a weak influence on the effective properties.The effective modulus and the Possion's ratio have a positive and negative correlation with the modulus of matrix,respectively.With the increase of Possion's ratio of matrix,the effective modulus would first increase and then decline at small scale and the effective Possion's ratio increase approximate linearly.Although the study of this dissertation is still in its infancy,it will,as the study continues,provide a new approach to estimate the mechanics properties of solid propellant and accelerate the study process of the solid propellant with high mechanical properties.