X-cor夹层结构低速冲击实验和数值模拟研究

X-cor泡沫夹层结构是一种通过Z-pin技术增强泡沫夹芯的新型高性能夹层结构。在低速冲击下,X-cor夹层结构损伤失效机制复杂,通过在不同能量阶段对X-cor夹层结构失效行为进行分析,讨论Z-pin植入体积分数和泡沫芯材密度对失效行为的影响。低速冲击试样规格为Z-pin直径0.5 mm、植入角度为22°,分别改变泡沫类型和Zpin植入体积分数进行实验,结果表明:6 J冲击能量下,冲击能量主要由面板分层承担,相对于未植入Z-pin试样,随着Z-pin植入体积分数的升高,面板分层面积最多减少了45.1%,而泡沫密度对分层面积影响不大;12 J冲击能量下,部分Z-pin发生失效,通过剩余压缩强度比发现,随着Z-pin植入体积分数的增加,剩余压缩强度比先增大后减小,植入体积分数为0.42%时最高,而此时泡沫密度增加,剩余压缩强度比也随之增加;当能量到达18 J时,芯材开始出现剪切裂纹,同时吸收大部分能量,较弱的芯材剩余压缩强度比大,而Z-pin植入体积分数越大,剩余压缩强度比反而越小。采用数值模拟的方法建立低速冲击模型,并将冲击后的结果直接传递应用于剩余压缩强度模型中,得到的结果比实验值偏高25%~29%。

Experimental and Numeral Investigation on X-cor Sandwich Structure under Low-velocity Impact

X-cor sandwich is a new kind of foam sandwich reinforced by Z-pin techniques.Under low velocity impact damage,failure mechanism of X-cor sandwich structure is complex.Failure behavior of X-cor sandwich structure at different energy stages was analyzed,and the effects of the volume fraction of Z-pin implant and the density of the foam core on the failure behavior were also discussed.Z-pin diameter of specimens in low speed impact test was 0.5 mm,and the implantation angle was 22°,and the type of foam and Z-pin implant volume fraction in the experiment was variable.The results show that under 6 J impact energy,the impact energy is mainly absorbed by the panel's delamination.The sandwich contained Z-pin is beneficial to reduce the delamination area,while the delamination area of blank sample increases by 45.1%.The foam density has little effect on the delamination area.The Z-pin fails under 12 J impact energy.The residual compressive strength ratio increases first and then decreases with the increase of volume fraction of Z-pin.The sample has the highest residual compressive strength ratio when the volume fraction reaches 0.42%.As the foam density increases,the residual compressive strength ratio increases.When the energy reaches 18 J,shear crack appears in the foam core,and the crack absorbs most of the energy.The weaker the foam core,the larger the residual compressive strength ratio is,and the more the volume fraction of Z-pin implanted,the lower the residual compressive strength ratio is.The low velocity impact model is also established by numerical simulation,and the result of impact damage is directly transferred and applied to study the residual strength model;the result obtained is 25%~29% higher than the experimental value.