Study On Cushioning Characteristics Of New Sandwich Packaging Materials

With the development of transportation packaging,the existing cushioning materials mainly include paper cushioning materials,foamed plastic cushioning materials and so on.Among them,the sandwich layer structure of sandwich panel cushioning packaging has an important influence on cushioning performance.Fractal structure is a special geometric figure.Fractal structure has the advantages of self-similarity,multi-scale symmetry and compact structure.Fractal theory is widely used in structural unit design in different fields,such as mechanics,chemistry,electromagnetism,forestry and so on.Because fractal structure has strong space filling ability and recurrence relation,it can achieve distinctive effect when used in buffer structure.In this study,based on Hilbert fractal structure,through parametric modeling,using the string rewriting technology based on LOGO language,and expressing the generation mechanism of fractal by L(Lin’s)language,Hilbert fractal theory is formed into a recursive formula and a third-order model is formed.Using Solid Works software,the 3D model is designed,and the Hilbert fractal structure model is prepared by 3D printing technology.Quasi-static compression and dynamic impact tests were carried out to test the mechanical properties of Hilbert fractal structure.According to the physical characteristics of thermoplastic polyurethane materials,the Yeoh second-order constitutive model is constructed,and the material properties are verified in ANSYS Workbench software.At the same time,the cushioning performance of Hilbert fractal structures with different orders and layer thicknesses is simulated by finite element method.Taking the energy absorption per unit mass(SEAm)as the objective parameter,the structural response surface optimization was carried out to find the most suitable Hilbert fractal structure.Compared with the common "m" structure,it highlights the structural advantages of Hilbert fractal structure.The research shows that based on the uniaxial tensile data of thermoplastic polyurethane material,the Yeoh two-parameter constitutive model is established,and the error between the static compression result and the experimental data is 8%,which verifies that the finite element method can guide the design of sandwich structure.At the same time,in the static compression test,when the fractal factor(n)is 2.5 and the unit layer thickness(t)is 0.75 mm,the energy absorption per unit mass reaches 0.0076J/g,and the effect is the best.Compared with the rice-shaped sandwich structure,the Hilbert fractal structure of total energy absorption increased by 120% and the energy absorption per unit mass increased by 72%.In the dynamic impact test,when the fractal factor(n)of Hilbert fractal sandwich structure is 2and the unit layer thickness(t)is 1mm,the energy absorption per unit mass reaches 0.0024J/g.Compared with the rice-shaped sandwich structure,the Hilbert fractal structure increases the total energy absorption by 98% and the energy absorption per unit mass by 26%.Compared with ordinary plastic plates,the energy absorption is obviously improved,which is of practical significance for the development and application of new cushioning packaging structures.