Research On The Strain Rate Effect Of Rigid Polyurethane Foam

Rigid polyurethane foam（RPUF）is a polymer material with insulating properties.Because of its light weight,high compressive strength,low thermal conductivity and low water absorption,it is widely used in aviation,construction and other military fields.At the same time,because high-density rigid polyurethane foam has good energy absorption characteristics,it has been used as a wave-absorbing and energy-absorbing material in anti-explosion and impact resistance in recent years.Therefore,research on the mechanical properties of rigid polyurethane foam has been carried out,and it is the mechanical response under load provides necessary constitutive models and material parameters for structural design,which has important academic significance and engineering value.This paper has carried out a series of research work on the mechanical properties of high-density rigid polyurethane foam under different loads.Firstly,through a series of quasi-static compression mechanical performance tests with a strain rate of 10^-4-10^-2/s on high-density RPUF materials,including quasi-static compression tests and triaxial confining pressure tests.The quasi-static mechanical properties parameters such as compressive strength and tensile strength and corresponding stress-strain curves of RPUF materials under different stress states were obtained.The mechanical response characteristics and damage evolution mechanism of materials under quasi-static loading are discussed.Then the dynamic compression experiments with a strain rate ranging from 1000/s to 2300/s were carried out on rigid polyurethane foam（RPUF）using a split Hopkinson pressure bar（SHPB）with a diameter of 37mm.The experimental results show that the RPUF material has a significant strain rate effect.Lay the foundation for the research on the constitutive model of high-density RPUF materials.Secondly,the RPUF material is regarded as an ideal elastoplastic model without strain rate effect,and the finite element software ABAQUS is used to carry out the numerical simulation of the SHPB experiment of the RPUF material.The simulation results show that the dynamic yield strength of the RPUF material increases with the increase of the strain rate and the influence of transverse inertia effect on the experimental results cannot be ignored.Then based on the experimental data of triaxial confining pressure,it is found that the yield strength of RPUF material has a linear relationship with hydrostatic pressure.Therefore,it is necessary to consider the influence of the hydrostatic pressure effect of the material itself when studying the strain rate effect of RPUF material.Next,in order to obtain the actual strain rate effect of RPUF material,a constitutive model including hydrostatic pressure effect and strain rate effect was proposed based on the experimental data of SHPB and triaxial confining pressure.The parameters were revised and applied to the SHPB numerical simulation of RPUF materials.The simulation results were consistent with the experimental data,indicating that the proposed constitutive model and the revised material parameters can truly reflect the mechanical properties of the RPUF material itself,thereby obtaining RPUF The actual strain rate effect of the material.In addition,the high-density rigid polyurethane foam material was subjected to dynamic compression experiments at high temperature.A constitutive model suitable for high-density RPUF materials at different temperatures is established based on experimental data.The constitutive model considers the effects of strain,strain rate and temperature on yield strength and flow stress,and can be within a wide range of temperature and strain rate The yield strength and flow stress of RPUF materials are predicted.Finally,the plastic stress-strain curve calculated by this constitutive model is compared with the experimental results to verify the accuracy of the proposed constitutive model.Finally,through quasi-static compression experiments and triaxial confining pressure experiments,compression experiments were carried out on RPUF materials with different densities,and the yield strength,elastic modulus and other quasi-static mechanical performance parameters of the material under low strain rate,and the failure form of the material were obtained.Then,the SHPB experimental device was used to carry out high-strain rate experiments to obtain the stress-strain curve of the high-strain rate material,which is used to analyze the influence of the sensitivity of the material density to the strain rate.The above work has important guiding significance for the structural design and optimization of rigid polyurethane foam.