Research On The Performance Of 3D Printed PLA-Cu Composite Liner

The low-density material liner has achieved excellent results in the aspect of ’realizing the penetration of explosive reactive armor without explosion’,and has gradually become one of the research hotspots in the field of anti-explosive reactive armor.For the preparation of lowdensity liners,people have proposed processing technologies such as turning,cold-pressing sintering,compression moulding,and hot-pressing.3D printing technology is a high-end digital manufacturing technology that has developed rapidly in recent years.It is also known as additive manufacturing technology.It adopts digital modeling and parametric technical methods to effectively control the printing accuracy while reducing the cumbersome processing steps of traditional processing technology.It can meet the requirements of rapid prototyping and is suitable for preparing high-precision liners.In this paper,low-density liners of polylactic acid(PLA)and copper powder filled polylactic acid(PLA-Cu)were prepared by 3D printing technology.The process of jet forming,penetration of target plate and impact initiation of explosive reactive armor of PLA and PLACu liners under detonation load was studied by numerical simulation and experimental verification.The specific research contents and conclusions are as follows:(1)The anisotropic behavior of PLA and PLA-Cu materials in 0°(horizontal)and 90°(vertical)directions,as well as the mechanical properties under dynamic and static load compression were tested by universal material testing machine(CMT5105)and split Hopkinson pressure bar(SHPB).The results show that the tensile direction can significantly change the toughness and brittleness behavior of the material,and then affect the mechanical properties of the material.The stress-strain curves of the two materials under static compression are similar to those of porous materials,including three stages of linear elasticity,yield stress platform and densification.The stress-strain curve of PLA material under dynamic compression is similar to that under static compression,while PLA-Cu material has obvious ’impact embrittlement’ phenomenon,which leads to the rapid decrease of its dynamic stress-strain curve after passing the yield point.In terms of strain rate sensitivity,it is found that both materials are strain rate insensitive materials at the strain rate of the same magnitude,but they have obvious strain rate effect during the transition from static to dynamic.(2)The Johnson-Cook and Sherwood-Frost constitutive models with Cowper-Symonds strain rate terms were obtained by fitting the static and dynamic compression test data.The Du impact insulation line of the material was obtained by symmetrical collision test.Based on this,the polynomial Grüneisen high-pressure state equation and Grüneisen coefficient of the two materials were obtained by theoretical calculation,which provided model data support for numerical simulation of jet forming and penetration of 3D printing liner.(3)The SPH algorithm was used to calculate the jet forming process of PLA and PLA-Cu liners.It was found that both jets obviously showed the characteristics of ’expansion particle flow’,and the jet shape was similar to ’hyperbola’.With the increase of time,the expansion degree of the jet to the surrounding also increased.The real morphology of the two material jets was obtained by pulsed X-ray experiments,which verified the effectiveness of the numerical simulation.The theoretical analysis shows that there is gasification phenomenon in the head of PLA jet during the forming process,and the length of gasification part accounts for about 21%of the total length of jet.(4)The results of steel target damage show that the penetration depth of PLA and PLA-Cu jets is about 7mm at double and three times stand-off.The entrance and bottom diameters of penetration aperture at double stand-off are 26mm,16mm and 30mm,17mm respectively,which are reduced by 15.4%,37.5%and 23.3%,23.5%respectively at three times stand-off.Compared with the damage results of the steel target at twice stand-off,the entrance diameter,bottom diameter and penetration depth of the aluminum target penetration aperture by PLA and PLA-Cu jets are increased by 34.6%、25.0%、171.4%and 16.7%、5.9%、257.1%,respectively.The analysis shows that the damage power of PLA-Cu jet is stronger than that of PL A jet,and the damage effect on aluminum target is better than that of steel target.(5)Based on the numerical simulation results,it is found from the initiation mechanism analysis that the impact initiation of PLA-Cu jet on explosive reactive armor is mainly affected by the precursor shock wave,and the source of the precursor shock wave is mainly composed of three parts:the initial impact loading of the explosive by the ’circular’ jet head which bypasses the plug block,the impact of the plug block,and the continuous impact of the jet neck on the explosive.It is found that the p2 τ criterion is more suitable than the v2d criterion as the initiation criterion for the impact initiation of the 3D printed PLA-Cu liner.The p2 τ initiation threshold of the explosive in the explosive reactive armor is 239.582GPa2·μs.(6)The experimental results show that the PLA-Cu liner realizes the ’penetration without explosion’ into the explosive reactive armor at twice and three times stand-off,and makes the explosive layer fail in a large area under the impact of the jet,which achieves the effect of removing the interference of the explosive reactive armor for the subsequent main jet.Therefore,3D printed liner has a better application prospect in the damage of light armor at lower stand-off.