Study On The Damage Resistance Of Honeycomb Sandwich Structures With Thin Facesheets Subjected To High Velocity Impact

Composite sandwich structures have been widely used in the industryof aeronautics and astronautics. Visible damage and even penetration areeasily found in sandwich panels with thin facesheet impacted at relativelylow energy. From the perspective of structural durability design, impactresistance research of the honeycomb sandwich panel is of greatsignificance.Firstly, the flatwise compressive tests were carried out on sandwichspecimens. Then the mechanics properties of NOMEX honeycomb paperwere obtained through the cellular equivalent mechanical propertiesresearch. An effective finite element model had been created by selecting aunit cell with symmetry boundary conditions. The flatwise compressiveprocess and the failure of the honeycomb core were simulated andanalyzed using the model. Secondly, specimens of different facesheetthickness were tested via dropping weight method at various levels ofimpact energy using two impactors of different mass. The effect of impactvelocity, impact energy and panel thickness on the shock response andfailure mode were analyzed. Thirdly, a finite element model of compositesandwich structures with thin facesheets subject to impact loading werecreated in ABAQUS software. The constitutive model of the compositewoven fabric material was defined in the VUMAT subroutine with theconsideration of progressive damage process. Two typical failure modewere simulated in ABAQUS/EXPLICIT solver. The simulation resultswere in good agreement with the experimental results, which verified the validity of the finite element method. Then the damage process andmechanism of the impact were analyzed using the correct model.The results reveal that the maximum contact force increases with theimpact energy when the energy is relatively low, while it will be constantafter it reaches the threshold value. Fiber fracture and penetration willemerge as the impact energy increases, whereas the dent in the facesheetand slight delamination around the impact center were the major failuremode at low impact energy. The impactor will rebound and the curve ofcontact force versus time has no platform when the facesheet wasun-penetrated. While in the penetrated cases, the impactor doesn’t reboundand there is a platform in the curve of contact force versus time. Besides,the bigger mass impactor will lead to longer contact duration and biggerdent depth under the same impact energy after the maximum contact forcereaches the threshold value.