The Study On Penetration Performance And Failure Mechanism Of The Sandwich Plate With Shear Thickening Fluid Core

The sandwich structure consists of face-sheets and core.It has a wide application inthe field of structural engineering,aerospace,transportation,and safety protection due to its excellent properties,such as low specific mass,high specific stiffness and high energy absorption etc.With the development in these fields and the growing demands,the design and preparation of the core materials in the sandwich structure have become the focus of researches on sandwich structure.Shear thickening fluid（STF）consists of a stabilized dispersion of hard nano-particles in a carrier solvent,and its viscosity can increase immediately,even into solid-like state when subjected to impact loading,and then recover when the impact loading is removed.Lots of energy is dissipated in the process of shear thickening.STF attracts wide attention in the field of damping and noise reducing,safety protection.STF was proposed to act as the core of the sandwich structure,and its properties of penetration and energy absorption were studied.The split Hopkinson pressure bar system were revised to perform the dynamic penetration experiment of the sandwich plate with STFs core.The failure modes of the sandwich plate with STFs core were obtained under different penetration velocity,and the failure mechanism was analyzed.The properties of energy absorption of STFs were also discussed under different penetration velocity.Based on the results from experiments,the numerical simulation was conducted by ANSYS/LS-DYNA to study the propagation of the stress wave of STFs in the process of dynamic penetration,and compare the failure mechanism obtained by simulation with that obtained by experiment.The results are as follows:（1）The SiO₂ nano-particles,of which the diameter is about 350 nm,was fabricated by Stober methods.The STFs with SiO₂ volume fraction of 54%and 56%were prepared.The maximum viscosity of 54 vol.%and 56 vol.%STFs is about 159 Pa·s and 465 Pa·s in the shear thickening process,respectively,which showed obvious shear thickening behavior.The sandwich plates with these two kinds of STFs as core were prepared.（2）The results of the penetration experiment showed that the failure modes of symmetrical and asymmetrical sandwich plates were different.The failure modes of symmetrical sandwich plates were petal failure.However,the failure mode of asymmetrical sandwich plate was plug failure mode when the velocity of projectile was less than 80m/s,and was petal failure mode when the velocity of projectile was more than 90m/s.The energy absorption of the sandwich plates with STFs core increased with the increasing impact velocity of the projectile.By the impact velocity of the projectile increasing,the resistance to the projectile increased due to the shear thickening effect,and the energy absorption efficiency of the STFs was improved.（3）The numerical results showed that the stress wave is obviously attenuated during the propagation process in the STFs.In addition,due to the movement of projectile in the shear thickening fluid,the shear thickening effects of STFs happened,and the pressure in the front of the STFs increased,which significantly decreased the velocity of the projectile.Furthermore,under the impact of the high-viscosity STFs promoted by the projectile,there is large deformation of the rear face sheet of the symmetrical sandwich panel,leading to the panel crack and petal failure.The rear face sheet of the asymmetrical sandwich presented small deformation and then plug failure under the impact of the projectile at low impact speed.When the projectile penetrate the asymmetrical sandwich at a high speed,the rear face sheet of the asymmetrical sandwich presented large deformation and then petal failure under the impact of the STFs promoted by the projectile.