Impact Behavior of Metal Sandwich with Corrugated Cores

Author:Cao Bing Tuo

Supervisor:zhao han


Degree Year:2018





Corrugated core sandwich combining both lightweight and energy absorbing capacities have attracted many academic interests in the past decades.A great number of investigations on various aspects of corrugated core sandwiches are reported,including the structural response under static compression loading,three-point bending loading and impulsive loads incident from water.In addition,as a typical energy-absorbing structure widely used in the aviation industry and rail transit,it is important to understand the mechanical behavior of the corrugated sandwich under static and impact loading.Meanwhile,the optimization designs as well as widespread application of gradient materials in corrugated sandwiches have been paid more attentions due to their advantages of resistance to impact.This paper experimentally and numerically investigates mechanical behavior,including the response and failure mechanism of single layer,multi-layer and gradient corrugated sandwich structures under static and impact loadingThis dissertation includes two parts: in the first part,the experimental and numerical investigations on the mutilayer sandwich with corrugated cores are conducted.In the experimental study on sandwich,the manufacturing process of corrugated core is presented at first,and then the single layer,parallel and perpendicular multilayer sandwiches with corrugated cores are built.Experimental results on single layer as well as multilayer sandwiches show that peak forces under impact load is obviously higher than that of static.Such an enhancement is believed purely due to the structural effect-micro inertia considering the base material of AL1060 is a non-rate sensitive material.Furthermore,the bending of interlayer in parallel multilayers sandwiches may affect the deformation mode and reduce the force oscillation during successive folding.Lastly,there are three deformation modes of multilayer sandwiches under different impact velocities.At low velocities,the yield strength of layers plays a dominate role in the deformation,with collapse bands initiating from the weakest layer and propagating layer by layer.At moderate velocities,it is the combination of yield strength and inertial effect that takes a crucial role,with collapse generating from all layers at the same time.At high-velocities,the effects of inertial effect become more pivotal in the deformation mechanism,with shock bands concentrated near the imposed side.The second part investigates the mechanical behavior of gradient sandwich experimentally and numerically.Four gradient profiles named C3456,C6543,C3663 and C6336 are designed based on the concept of gradient material.The deformation modes and failure mechanism of them are investigated by experimental(including direct impact Hopkinson bar,Taylor test)and numerical methods,where the direct impact Hopkinson bar is applied to measure the force of distal end,with the Taylor test used to scale the force of impacted end.By the finite element method,different deformation modes and mechanism of four graded sandwiches are obtained.Results show that there are three distinct mechanisms governing the response of the sandwiches.The yield strength and inertial effect are the crucial factors influencing the structure deformation under low-speed impact,with the weaker layers buckled at first;at medium velocities,the combination of inertial stabilization,yield strength and plastic wave has a combined effect,with the structure destoried from the impacted end/ weaker layer;at high velocities,plastic wave effect plays a leading role and the structure crushed from impacted to distal end layer by layer.At last,a general principle for the design of the multilayer sandwiches with corrugated cores to improve energy absorption efficiency is proposed,which consists of placing the weaker layers near the protected structure and the harder layers near the impacted end of the sandwich.