| Considering that the end-trabecular beetle elytron plate with new type biomimetic material(honeycomb plate with trabecula located at the joint of the honeycomb wall,EBEP)has excellent compressive and energy absorption capacity,and the fact that about 10%of trabeculae are distributed at the middle of the honeycomb walls,this research will focus on the beetle elytron plate with trabecula located at the joint of the honeycomb walls,i.e.middle-trabecular beetle elytron plate(MBEP).First,the influences and its mechanism of η(ratio of trabecular radius rt to length of honeycomb wall L),one of the horizontal structural parameters,on the fundamental mechanical properties of MBEP are investigated;Then,the effects and its mechanisms of vertical structural parameters,namely ξt(ratio of trabecular chamfer radius rc to trabecular radius rt)and β(ratio of core height h to wall thickness T in core)are studied.Finally,the application research of MBEP in the field of car anti-collision is conducted by designing and manufacturing two types of beetle elytron plate with metal and optimizing the amplitude A of the deformation guide line.This research will provide both theoretical and the experimental foundation for the optimization of beetle elytron plate models and its relevant products and the application of them in the buffering and energy absorption field.Main conclusions are as follows:(1)The influences and its mechanisms of horizontal trabecular parameter on the compressive properties of the MBEPMBEPs are molded by 3D printing technology using material of resin.By experiment,we find that,when the trabecular radius is small(η=0.1),the compressive strength and energy absorption capacity of the MBEP exceed those of the honeycomb plate by factors of 2.2 and 3.3,respectively.These increases are greater than those of the EBEP;with an increase to η=0.15,the compressive strength remains nearly the same,while the energy absorption capacity continues to rapidly increase.The reason for this behavior is that the area in which there is a right angle at the interface between the core(trabeculae)and the skin is larger than the convex and concave regions inΦ-type deformations of the trabeculae,and thus,the capacity to resist deformation is greater.At the same time,by analyzing the deformation and failure mode of the trabeculae and comparing it with the EBEP,the strengthening mechanism that gives rise to the compressive properties of the MBEP is proposed as follows:the trabeculae are located at the center of the honeycomb walls,where the maximum deformations would otherwise occur;they constrain the deformation of the honeycomb walls;and the number of trabeculae in the MBEP also exceeds that in the EBEP.(2)The influences and its mechanisms of vertical parameters on the compressive properties of the MBEPThe conclusion,the compressive strength of both BEPs is approximately two times that of the honeycomb plate,is valid in a wider range of β and ξt,while only the EBEP has many failure modes and its stress-strain curve can form a plateau with reasonable structural parameters thus increasing the structural ductility.The MBEP,however,cannot form a plateau with any structural parameter in the condition of this part of research.The reason is that the torsional deformation of the triangular trabecula in the MBEP will reduces its buckling stability and weakens the trabecular-honeycomb synergistic mechanism.But this also makes it easier for the core layer to be dominated by overall buckling mode,which is more stable less sensitive to the changes in height and chamfer radius than the EBEP.Therefore,the MBEP has more stable deformation mode,easy manufacturing,no need of chamfers and other application conveniences,while the EBEP needs to add chamfers in its trabeculae during manufacturing,and must satisfy that ξt value is not less than 1.5 and β value is less than or equal to 21,to fully exert the mechanical characteristics of high strength,high energy absorption and high ductility of beetle elytra.In addition,for the first time,it is proposed that the trabecular chamfers has an significant mechanical function to improve the ductility of the Allomyrina dichotoma elytra,and experiments have verified that ξt value is at least 1.5 to fully play its role,which is highly consistent with the biological phenomenon in the Allomyrina dichotoma elytra.It is also explained from a mechanical aspect that the phenomenon that 90%of the trabeculae are located at the joint of honeycomb walls is to coordinate the existence of chamfers,maximize the mechanical properties of elytra,and achieve the purpose of lightweight and high-strength structural characteristics.(3)The energy absorption capacity and application research of MBEPThe optimized amplitude A=1.0 of the deformation guide line of MBEP crash box is proposed.At this time,the laminated compression deformation is more stable and the peak force is almost the same as the conventional crash box,while the energy absorption value and energy absorption efficiency are both increased to more than 3 times.In addition,it is proved that the larger the amplitude A,the higher the energy absorption efficiency,and the peak force is also closer to the conventional crash box,which provides an approach for adjusting the mechanical properties of the crash box according to different designing requirements in specific engineering.Experiments reveal that there is cracking failure in the conventional crash box;however,the coordinated and uniform S-typed laminated compression deformation is developed in both the MBEP and the EBEP crash boxes.At the same time,the force values of the conventional crash box during the main energy absorption stage fluctuate at a low level,greatly reducing the energy-absorbing efficiency.In contrast,the MBEP and the EBEP crash boxes exhibit higher force values during the same stage and tend toward stability after a rising stage.Therefore,the MBEP and the EBEP have excellent deformation and energy absorption capacity. |
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