Research On The Mechanical Properties And Constitutive Model Of Composite Propellant

As a kind of solid propellant,HTPB propellant is widely used due to its high energy,high density and good comprehensive performance.In order to provide the reference for solid rocket motor propellant grain structural integrity analysis and optimal design method,the mechanical properties and constitutive model of the composite propellant was researched.This paper selects HTPB propellant as the research object,and the main research contents and corresponding results include the following aspects:(1)The quasi-static compression experiments for HTPB propellant were carried out at different temperatures(10?,30? and 50?)and different strain rates(3.33×10-4s-1,3.33×10-3s-1,3.33x10-2s-1 and 3.33×10-1s-1).And the dynamic compression experiments for HTPB propellant were carried out at different strain rates(2500s-1,3500s-1 and 4500s-1).The mechanical behaviors of HTPB propellant at low strain rates and high strain rates were analyzed,the results show that the mechanical behaviors of HTPB propellant were dependent on temperature and strain rate at low strain rates and were dependent on strain rate at high strain rates,and the initial compression modulus increased with either temperature decreasing or strain rate increasing,and the relationship between yield stress and logarithm of strain rate was linear at low strain rates,and the relationship between peak stress and logarithm of strain rate was also linear at high strain rates.(2)Based on Sherwood and Frost constitutive framework,the constitutive model considering the influences of environmental temperature was proposed for HTPB propellant at low strain rates,and the model-predicted curves at different temperatures and different strain rates were obtained.Comparisons of the model-predicted curves and the experimental ones indicates that the Sherwood and Frost constitutive framework model can well predict the stress-strain characteristics of the HTPB propellant at different temperatures(10?-50?)and different strain rates(10-4s-1-10-1s-1).(3)The modified ZWT constitutive model was proposed through replacing the polynomial nonlinear elastic term in ZWT model by hyperelastic response item,and the model-predicted curves at different strain rates were obtained.Comparisons of the model-predicted curves and the experimental ones indicates that the modified ZWT constitutive model can well predict the mechanical properties of the HTPB propellant in large strain which maximum range can reach 0.45 and it can also reflect the stress-strain characteristics of the HTPB propellant at different strain rates varying from 10-4s-1 to 103s-1.(4)The temperature rise results of HTPB propellant resulted from deformation-induced heating effect at high strain rates(2500s-1,3500s-1 and 4500s-1)were obtained by experimental measurement and theoretical calculation respectively,and the function which expresses the temperature rise of HTPB propellant resulted from deformation-induced heating effect was proposed based on results above.Research results show that the temperature rise result obtained by theoretical calculation was true temperature rise result and the temperature rise function based on the true temperature rise result can well predict the temperature rise of HTPB propellant resulted by deformation-induced heating effect at different strain rates(2500s-1,3500s-1 and 4500s-1).(5)Revising the modified ZWT constitutive model by adding the thermal softening function which can reflect the thermal softening effect of deformation-induced heat to original model,the modified ZWT constitutive model considering the deformation-induced heating effect for HTPB propellant at an initial temperature 10? was proposed.Research results show that the addition of thermal softening function can well revise the prediction of the modified ZWT constitutive model to the mechanical properties of the HTPB propellant at high rates so that the model can well comprehensively predict the stress-strain characteristics of the HTPB propellant under a wide strain rate range.