Numerical Simulation Of Strain Rate Effect With Fiber Reinforced Composite

Fiber reinforced composites are widely used in automotive,aviation,military and other important fields because of their excellent specific strength and modulus characteristics.These materials will inevitably be impacted by foreign bodies such as birds,missiles,gravel and so on.It is necessary to study their mechanical properties under impact conditions.In order to study the mechanical properties of an object under impact,it is a simple and convenient method to use finite element numerical simulation.At present,the static mechanical simulation of composite materials has been relatively mature.However,due to the strain rate effect of composite materials,the dynamic simulation accuracy needs to be improved.In the existing composite constitutive model,only the viscoelastic model considers the strain rate effect,and the model can only be used in the shell element,and the solid element is limited.The finite element software Abaqus is superior in the secondary development of the material constitutive model.The VUMAT subroutine interface is mainly used for secondary development of material models in transient explicit analysis.In the existing research results,most of the exploration of the strain rate effect of composite materials is based on experiments,and the experimental results are integrated into empirical formulas and material models that can be used by more people,finally applied to finite element software.Fewerly,the composite model considering strain rate in existing commercial finite element software is limited.Therefore,it is necessary to use the method of writing subroutine to establish a three-dimensional composite constitutive model considering the strain rate to improve the dynamic simulation accuracy of the composite.Based on the above discussions,this article specifically studied the following.(1)In the constitutive model of fiber reinforced composites,the strain rate correction formula is added.In order to make the simulation of the composite material in the field of dynamic impact more accurate,the strain rate effect needs to be considered in the material constitutive model.The model mainly includes seven kinds of damage criteria,six stiffness degradation parameters,elastic modulus and strain rate effects of strength.Moreover,the strain rate effect in this model is different from the viscoelastic model,which can be used forsolid elements.The elastic modulus and strength values in different directions are affected by the strain rate in the corresponding direction.(2)The paper associates Abaqus 6.14,Intel Visual Fortran 2013,Microsoft Visual Studio 2013,and compiles the constitutive model proposed in the first part into a VUMAT subroutine using Fortran language,embeding Abaqus software for trial debugging and finite element simulation.(3)The material model proposed in this paper is applied to the finite element model of projectile penetrating laminate for validity verification.According to the experimental model,the finite element model of the projectile penetrating composite laminate is established,and the material model proposed in this paper is verified.The results show that the material model established in this paper is effective,and the simulation results of the constitutive model with strain rate are about 15% larger than the strain rate at the same time.(4)The paper studies the effects of strain rate effects on simulation accuracy under different penetration speeds,laminate thickness and projectile diameter.The finite element simulation is used to study the influence law of different parameters on the sensitivity of variability.It is found that the higher the strain rate effect sensitivity with the increase of penetration speed and the diameter of the projectile,the greater the influence of the strain rate on the simulation results in the constitutive model;on the contrary,the strain rate sensitivity decreases with the increase of the thickness of the laminate.(5)The paper applies the constitutive model of this paper to the composite hood collision model,comparing the simulation results with the head damage degree(HIC)of the actual collision point.