Dynamic Behavior Of Titanium-aramid Honeycomb Sandwich Panel Subjected To Intensive Impulse Loading

High-pressure shock waves can be induced by intense pulsed laser,particle beam,hypervelocity collision and so on.Such loads are characterized by high amplitude and short duration(generally peaks greater than 1 GPa and widths less than 1?s).How to weaken the damage caused by intense short impulse loading has been concerned by major countries in the world.The application of new materials and new structures is the fundamental method to greatly improve the impact resistance.Aramid honeycomb,with excellent low density,flame retardance,radiation resistance and high strength properties,has been adopted as cores for high-performance aviation sandwiches.Titanium alloy,as an important structural material in the aeronautic and astronautic industry,provided light density,high specific intensity and excellent resistance to corrosion.The sandwich panel composed of titanium alloy plate and aramid honeycomb core has important application value in aerospace industry.Research on dynamic response of titanium-aramid honeycomb sandwich panels under intense impulse loading and revealing its deformation and failure mechanism are the basis of engineering application research and material design research of aramid honeycomb materials,which has great importance in scientific research and engineering application.In this paper,the plastic dynamic response of TC4 titanium alloy-aramid honeycomb sandwich panel under intense impulse loading is studied systematically by means of experimental research,theoretical analysis and numerical simulation.Specific research contents and results are as follows:The deformation/failure modes and impact resistance of sandwich panels subjected to intense impulse loading by using the electric gun method,are investigated experimentally.A comparison of structural deformation resistance between sandwich panels and plates of equivalent mass is investigated,which shows that the impact resistance of sandwich panels can be efficiently improved because of crushed honeycomb cores and deformed front plates.Effects of impact velocity and boundary conditions on the dynamic response of sandwich panels are identified.The results indicate that fully clamped boundary reduces the damage extent of honeycomb cores and front plates,however,local plastic deformation of back plates increases.In addition,it is found by metallographic analysis that the location of the spall plane can be acquired from the free surface velocity,but the damage surface maybe in the stage of growth and coalescence of multiple voids.The dynamic response process of sandwich panels under two modes of spallation and plugging is divided into three stages:collision and spallation(plugging),honeycomb core compression and overall structural response.And the expressions of energy transfer in different stages are given.Based on the principle of energy balance,the approximate solution of the deflection curve of the back plate under intense impulse loading is derived by using a combined yield criterion taking account into plastic bending and stretching.Based on the above experiments,simulations are conducted with SPH-based internal structure model using the AUTODYN software.Here,the elasto-plastic constitutive is adopted to describe the mechanical behaviour of the core and corresponding matrix constitutive parameters are obtained quantitatively.An optimal particle size is determined by comparing the effects of different particle sizes on computational efficiency and accuracy.Afterwards,the proposed SPH model is validated with the experiments,making it feasible for following studies.Based on the established simulation model,the weakening effect of the core on the reflective pressure of front plate and the impact resistance of aramid honeycomb sandwich panel are studied.The spallation law of TC4 titanium alloy plate under intense impulse loading is studied by simulation.The following conclusions are drawn:In the velocity range of 2000 to 3000 m/s,the spall thickness decreases with the impact velocity and increases with plate thickness;In the propagation process of pressure pulse,the width of pulse peak is first attenuated,followed by pulse intensity;The pressure calculation formula(8_b_p_p only applies to the case where the width of pulse peak does not decay completely.The energy absorption characteristics of aramid honeycomb core under high-velocity impact loading are investigated using the ANSYS/LS-DYNA software.It is found that the mass specific energy absorption increases with side length and is basically not affected by foil thickness.The volume specific energy absorption decreases with the side length and increases with the foil thickness.More importantly,with the increase of the impact velocity,the energy absorbed by honeycomb core increases.When the back of the panel is covered with 0.5 mm and 1.0 mm thickness Kevlar material,the velocities of the scabs are about 50%and 30%of that of the uncovered.The velocities of the scabs decrease greatly.