Study On The Cushioning And Energy Absorption Characteristics Of Composite V Shaped Folded Core Sandwich Structure

As a lightweight sandwich structure,the composite sandwich structure with folded core has excellent mechanical properties.The open single cell design makes the internal cavities of the sandwich core pass through each other,which can make up for the shortcomings of the honeycomb and foam structure core confinement and help the discharge of moisture and heat inside the structure.The cavity of the middle core layer has the ability to produce large plastic deformation and can play a good buffering and energy absorption role when impacted.It is widely used in the design of energy-absorbing structures for transportation buffer systems.In this paper,the composite sandwich structure with folded core made of carbon fiber reinforced polymer（CFRP）laminate as the panel and aluminum V shaped folded core as the sandwich core is used as the research object to study the cushioning and energy absorption characteristics of the structure under low-velocity impact conditions.Firstly,for the diversified structural parameters of the V shaped folded core,a parametric model was established by using the finite element method.The deformation under compression load was analyzed,and the effects of single-cell geometric parameters on the equivalent compression stiffness,energy absorption and specific energy absorption were obtained by the controlled single-variable method,which laid the foundation for the subsequent research and optimization of the cushion energy absorption characteristics of the sandwich structure with folded core.The dynamic response of V shaped pleated sandwich panel of aluminum panel under low-velocity impact was analyzed.The low-velocity impact finite element model of aluminum pleated sandwich panel was established and the convergence of the model was tested,and the correctness of the model was verified by comparison with literature tests,which laid the foundation for exploring the cushioning energy absorption characteristics of CFRP panel-aluminum pleated core sandwich panel.Based on the previous modeling basis,combining the three-dimensional progressive damage failure model of CFRP panel and cohesive unit failure model,the finite element model of low-velocity impact of CFRP panel-V shaped folded core sandwich structure was constructed by the user subroutine.The damage,impact contact force and energy absorption of the sandwich panel under different impact energy were analyzed.A low-speed impact test platform for sandwich panels was built and different impact energies were tested.The correctness of the FEM simulation model was verified by comparing the contact force curves and deformation between the test and simulation.Finally,the effects of panel thickness t_f,core wall thickness t_c and core configuration parameters（V-line length B,V-line tension angleθ,serrated line angleδ）of the sandwich panel on the contact force,energy absorption（EA）and specific energy absorption（SEA）of the structure under low-velocity impact were further investigated using the validated FEM model.In order to improve the SEA of the structure,the quadratic polynomial response surface functions between the structural geometric parameters B,t_c,t_f,δandθof the folded sandwich plate and the peak impact contact force F_max and SEA were constructed using a Latin hypercube experimental design with selected sample points.An error analysis was used to verify the accuracy of the proxy model,and the main effects of each structural parameter on the target response were analyzed based on the proxy model.The multi-objective optimization of the proxy model was performed based on the multi-island genetic algorithm within isight software.The optimal solutions satisfying the constraints were obtained,t_c=0.246 mm,θ=46.63°,δ=62.75°,B=7.66 mm,and t_f=1.18 mm,the peak contact force of the optimized structure is reduced by only 3.04%,while the SEA is improved by 14.5%,indicating that the optimized structure has good energy absorption characteristics.