Study On Mechanical Properties Of Brittle Hollow Particle Composites Under Impact Load

Fly ash cenospheres has hollow thin-wall,enclosed and semi-enclosed micropore characteristics,and also has the advantages of low density,high specific stiffness and high specific strength.Fly ash cenospheres can not only make an material as fill,and can release the collapse space after monomer is broken,as buffer material has good pressure can be.In order to study the application of brittle hollow particle material accumulation body in buffer protection,the mechanical behavior and buffer characteristics of fly ash cenospheres,a typical brittle hollow particle material,were investigated under impact load.Then in this paper,a composite foam was prepared with large-sized fly ash cenospheres as the main component and rigid polyurethane foam as the binder,The mechanical properties and deformation mechanism are analyzed.The main contents of this paper are as follows.?1?Through the static compression experiment of fly ash cenospheres accumulation materials with different particle size distribution,and the compression strain of particle accumulation body was limited to 50%,the relationship between particle crushing rate and crushing mechanism and macroscopic strain rate effect of materials was analyzed.Results show that the strength of materials in different particle size of fly ash cenospheres under dynamic compression than the quasi static has obvious enhancement,in the 150s^-10.001s^-11 of LGs and LTs accumulation materials strength increased by 200%and 195%,respectively,in the 150s^-1300s^-11 LGs and LTs accumulation materials increased by 39%and 51.5%respectively,and the intensity of strain accumulation rate of the 800s^-11 fly ash cenospheres material strength and strain rate of 300s^-11 when compared to the strength of the fly ash cenospheres packing materials have not been obvious change;Under the same strain rate,the strength and energy absorbing effect of small-particle pellet packing materials are 40%and45%higher than that of large-particle pellet packing materials.The particle size analysis of the broken floating beads shows that with the increase of loading speed,the crushing rate and degree of crushing of LGs and LTs will increase,and the larger the particle size of fly ash cenospheres at the same loading speed,the higher the crushing rate will be.Through the analysis of Hardin crushing potential,it is shown that the relative crushing potential of drift-beads per unit energy decreases with the increase of impact velocity,and the energy utilization rate for drift-beads crushing decreases under dynamic impact,resulting in higher energy dissipation and stress levels of fly ash cenospheres under the same compression amount,which is manifested as the macroscopic strain rate effect.?2?Static compression and SHPB experiments were used to analyze the mechanical properties and deformation mechanism of the fly ash cenosphere polyurethane composite foam.Results show that,the compressive response of syntactic foam was characterized by three typical processes,that is,linear elasticity stage,plastic stress plateau stage and densification stage.The syntactic foam exhibited relatively stable plateau stress which benefit its application in protective engineering.With the density varying from 0.45g/cm³ to 0.6g/cm³,the plateau stress and the energy absorption performance increased with the density.It also implied that the variation trend of plateau stress followed the power function relationship with the relative density.By using aluminum honeycomb as the reinforcement,the quasi-static compressive strength and plateau stress increased about 20⁴5%and 10²5%,respectively.Moreover,the main failure mode of syntactic foam transformed from shear cracking to axial compressive deformation in reinforced material under quasi-static compression.In the strain rate range of 0.001s^-11500s^-1,the compressive strength of syntactic foam shown obvious strain rate sensitivity while the plateau stress changed marginally with the strain rate.However,for reinforced material,the compressive strength and plateau stress both exhibited significant strain rate dependence.In summary,the beneficial effect of using aluminum honeycomb as reinforcement can not only improve the mechanical properties of syntactic foam,but also improve its dynamic behavior.?3?An empirical constitutive model of fly ash cenosphere polyurethane composite foam was established,and compared with the experimental results,it can more accurately reflect the mechanical properties of the composite foam.Fly ash cenosphere were randomly generated by Matlab and established by the finite element analysis software LS-DYNA The bead arrangement and porosity are similar to the finite element model of fly ash cenosphere polyurethane composite foam,and its mechanical properties and deformation mechanism are analyzed.This paper analyzes fly ash cenospheres and its composite foam by means of numerical simulation and experiment,which has certain reference value for the analysis of mechanical properties and strain rate effect of brittle hollow particle material and composite foam,and provides a new idea for the comprehensive utilization of industrial solid waste fly ash cenospheres.