Research On Impact Resistance Of X-cor Sandwich Structure

The X-cor sandwich structure is a new foam sandwich structure which is reinforced by Z-pin technology.It has a wealth of design and can usually be used in navigation,aerospace,train and other fields.At home and abroad,the anti-impact performance of the X-cor sandwich structure has been reported little.In this airticle,firstly,study on the the anti-impact performance of X-cor sandwich structure through experiment to explore the failure mechanism during the impact,and make a system research on the effects of different design parameters of X-cor sandwich structure in the low-velocity impact;then simulate the X-cor sandwich structure of low velocity impact and impact after the residual compressive strength by means of finite element analysis;finally,three factors and three levels orthogonal test was designed to carry out the high-velocity impact experiments,analyse the ballistic limit and damage area,then get the optimal parameter combination of X-cor sandwich.In the low velocity impact test,there are including: 1 low drop hammer experiment,2 Infrared nondestructive test,3 compression strength test after impact(CAI).The experiment study on the four design parameters: foam type,Z-pin implant spacing,Z-pin orientation and Z-pin angle on the anti impact performance of X-cor sandwich structure,the results showed that under high energy impact,weaker core material absorbed more energy;in low impact energy range,reducing Z-pin implant spacing can significantly decrease impact delamination damage area;four-direction implant Z-pin is slightly better than the two-direction implant Z-pin;X-cor sandwich structure owns better impact performance when the Z-pin inserting angle is 22 degrees.Low-velocity impact model of X-cor sandwich structure was established by commercial finite element software ABAQUS,the elastic plastic constitutive model crushable foam is instructed to simulate foam sandwich,the Z-pin is simulated by nonlinear beam element by 2D Hashin Failure Criterion,a continuum damage constitutive composite panel model was established.After the impact on the sandwich structure by previous scholars,and directly transferred the impact damage of sandwich structure to predict the residual strength.A full numerical analysis wsa presented to simulate the failure process of compression after low-velocity impact for foam sandwich composites.The FEA results showed that the delamination obtained by simulation was close to the experiment results,and the deviation was not more than 10%;in high impact energy,foam make the most contribution in the impact energy absorption;in the residual compressive strength of the simulation,the force peak measured by side compression was higher than the experiment results.The optimum design parameters of X-cor sandwich under the high-velocity impact was studied through the orthogonal test of three factors(Panel thickness,foam type,Z-pin implant spacing)at three different levels.The results showed that: the thickness of the composite panel has the most influence on the ballistic limit,so increase the thickness will enhance the anti-impact capability,but it also bring weight to increase;the next is the Z-pin implant spacing,which reduced the damage area most,and the Z-pin spacing should be less than the impact of punch radius;increasing foam density has little effect on the ballistic limit and damage area;so the comprehensive consideration,the best design level by using the panel the thickness of 2mm,foam type 71 IG,Z-pin implantation spacing is 5× 5mm.