Damage Simulation On CFRP Winding Layer Of High-pressure Hydrogen Storage Cylinders Under The High Velocity Impact

As the storage core of hydrogen energy batteries,the degree of development of high-pressure hydrogen storage cylinders will directly determine the battery life of the car,and will also affect the wide-ranging layout of the promotion and application of hydrogen energy.Type Ⅲ and Ⅳhydrogen storage cylinders have the advantages of high performance and hydrogen storage density per unit mass.However,due its carbon fiber reinforced composite materials have the typical characteristics of poor impact resistance and complex damage forms,application advantages will be difficult to play and they will be great potential safety hazards once severely damaged with high-velocity impact.So it is imperative to design and optimize the high-velocity impact resistance of hydrogen storage cylinders based on strict safety requirements and how to accurately simulate the complex stress and strain state and damage evolution mechanism law of carbon fiber reinforced composite material layers under high-velocity impact conditions through finite element numerical simulation method to replace the expensive and demanding gunshot test method is hotspot in development research for hydrogen storage cylinders nowadays.This thesis introduces a progressive damage analysis model for composite materials under high-velocity impact based on the strain rate effect,takes into account the nonlinear behavior caused by high-rate loads,and improves the dynamic simulation capability of the damage evolution of the carbon fiber winding layer of the hydrogen storage cylinder under high-velocity impact conditions.The high-velocity impact damage mechanism is discussed from the perspectives of damage characteristics and impact resistance characteristics,which provides a reference for the design optimization and safety analysis of the high-velocity impact resistance of the hydrogen storage cylinder.Based on the above discussion,the main research contents of this thesis are summarized as follows:(1)Based on the basic theory of elastic mechanics of composite materials,this thesis starts with the microstructure of carbon fiber reinforced composite materials and establishes a mechanical model of carbon fiber and matrix components at high strain rates.In addition,the constitutive relationship,Hashin failure criterion and stiffness degradation theory of carbon fiber reinforced composite materials were updated by the strain rate correction factor.Moreover,the three-dimensional constitutive model for the progressive damage of carbon fiber reinforced composite materials under the high-velocity impact was established.(2)This thesis builds a compilation platform for Abaqus 2016,Intel Visual Fortran 2013 and Microsoft Visual Studio 2012,and uses Fortran language to develop the VUMAT subroutine on the basis of the constitutive model of high-velocity impact progressive damage of carbon fiber reinforced composite materials related to three-dimensional strain rate,which is used to embed Abaqus-Explicit explicit finite element software through the method of transient dynamics analysis for subsequent finite element simulation calculations.The subroutine improves the dynamic simulation capability of the damage and evolution of the carbon fiber winding layer of the hydrogen storage cylinder under high-velocity impact.And carried out the validity verification of the subroutine based on the data calculation example.(3)The thesis starts with the high-velocity impact damage analysis of the shell unit of the carbon fiber reinforced composite layer of the high-pressure hydrogen storage cylinder,and discusses the factors such as the fiber winding angle and others on the damage evolution mechanism of the balanced carbon fiber winding layer and the law of the ballistic impact performance.The results show that the direction of the long axis of the damage of the carbon fiber winding layer is consistent with the fiber direction of the layer farther from the impact point in the adjacent two layers.Within a certain bullet impact speed range,its anti-ballistic impact performance shows an apparent trend of first increase and then decrease with the increase of fiber winding angle and the ballistic impact resistance is the best when the winding angle is ±45°around.This research lays the foundation for the subsequent high-velocity impact simulation of carbon fiber reinforced composites considering the strain rate.(4)The thesis carries out the high-velocity impact damage analysis of the solid element of the carbon fiber reinforced composite layer of the high-pressure hydrogen storage cylinder considering the strain rate.By analyzing the damage characteristics of the cylinder composite material layer and the related parameters of high-velocity impact damage,the high-velocity impact damage mechanism of the carbon fiber winding layer of the hydrogen storage cylinder is further discussed.The results show that fiber fracture,matrix tensile shear and interlayer delamination are the main damage forms of carbon fiber wound layers under high-velocity impact.Within a certain range,compared with bullet speed and mass,bullet shape,diameter and carbon fiber winding angle have more obvious effects on high-velocity impact damage.This study provides a reference for the design and optimization of hydrogen storage cylinders against high-velocity impact.