Influence Of Fatigue Cumulative Damage On The Energy Absorption Properties And Inner Resonance Conditions Of Honeycomb Paperboard

Honeycomb paperboard is a type of commonly used paper cushioning energy absorbing material. Generally, it is subjected to out-of-plane compression, the constitutive relation curve in the long strain appears a longer plateau stress, the deformation in the platform stage can dissipate a great deal of impact energy, so as to achieve product protection role. The energy absorption characteristics of honeycomb paperboard are not only related to the mechanics of raw materials and the relative density of the structure, and also the vibration compression fatigue cumulative damage during the transportation process. This paper takes honeycomb paperboard as the research objection, the quasi-static compression is tested to achieve the static mechanical properties change through the fatigue compression. The mechanism of fatigue damage(FD) was analyzed. The mechanical properties, energy absorption properties, fatigue cumulative damage evolution, inner resonance conditions and packaging dynamics changes are systematic researched, based on the honeycomb paperboard materials in different thickness-to-length ratio and different initial pre-compression rate after fatigue compression mixed with research of experiment and analysis of theory method.(1) The compression properties of honeycomb paperboard in different thickness-to-length ratio, different compression and different initial pre-compression ratio are researched, Select three types of different thickness-to-length ratio typical honeycomb paperboard, different compression times and initial pre-compression rate under the condition of fatigue compression is tested respectively, then the fatigue specimens of quasi-static compression is tested. Through the analysis of the experimental data, and summarizing the variation characteristics of the mechanical properties and energy absorption properties with the fatigue cumulative damage: The results are shown that, with the same thickness-to-length ratio, the honeycomb paperboard plateau stress and the energy absorption per unit volume decrease with the increase of the number of fatigue compression; with the increase of the number of compressions, the stress of the energy absorption efficiency at the peak point is reduced, and the energy absorption efficiency decreased. With the different thickness-to-length ratio increasing, the thickness-to-length ratio bigger, the more influence fatigue effect on the plateau stress. At the late fatigue stage of fatigue compression, the plateau stress changes slightly with the increasing of the number of recycling compression times.Under different thickness, the plateau stress of the honeycomb board is sensitive before 30000 fatigue times, but the fatigue effect has little effect on the plateau stress from 30000 to 50000 times.Under the different initial pre-compression ratio conditions, the plateau stress can be divided into two stages demarcated by εp=25%. Under the same number of fatigue compression, The plateau stress is sensitive before εp=25% and FD has slight effect on plateau stress after εp=25%. With the initial pre-compression ratio increaseing, the change of phase slope compression after fatigue compression(initial Young’s modulus) is larger. Under the same number fatigue compression, the initial Young’s modulus decreases with the initial pre-compression ratio increasing. With the initial pre-compression ratio increasing, the energy absorption per unit volume has the large fluctuations FD before εp=25%, while it decreases slightly after εp=25%. Under different initial pre-compression rate, the decrease rate of peak point migration is much greater, and the energy absorption property is also decreased and more obvious than the different fatigue compression times.(2) A plateau stress model of predicting the fatigue effect of honeycomb paperboard is established. The model is based on the plateau stress in the standard test environment and fatigue damage degree of the cell wall thickness ratio of cell wall material. The axial compression and plateau stress of the honeycomb paperboard under different fatigue damage are studied experimentally. The experimental values of the plateau stress are compared with the fitting forecast values. The accuracy of the model is verified by the consistency of the experimental values and the forecast values.(3) The static mechanical behavior of honeycomb paperboard is simplified as a piecewise function. The energy absorption ability of honeycomb board is modeling segmented. By considering effects of fatigue damage to the honeycomb energy absorption properties, the theoretical model of energy absorption process under predicting different fatigue damage was established. Each stage of the energy absorption model is a simple function of thickness-to-length ratio, the yield strength and fatigue damage of the wall material in the standard test environment. The energy absorption curve and the optimal energy absorption point of honeycomb board under different fatigue damage are obtained by the model. The model can be used for the optimization of the energy absorption structure of honeycomb paperboard.(4) The honeycomb paperboard fatigue damage evolution model is establish, based on the cumulative fatigue damage evolution model of composite material and considering different pre-compression ratio of honeycomb paperboard under fatigue damage, selecting plateau stress after the fatigue cumulative damage as damage parameter. Using the plateau stress method and the evolution method, the fatigue cumulative damage failure limit of the honeycomb paperboard was calculated, and the fatigue failure life of the two methods was found. With reference to the fiber reinforced composite material fatigue failure limit S-N curve method and ?-N method by plateau stress method and evolution method, the honeycomb paperboard in different pre-compression ratio ?p-N curve in the case, the ?p-N model is obtained by least square method, verify its effectiveness.(5) Containing the key parts of the two degree of freedom system packaging model is established, the variational iteration method(VIM) of different iterative criterion can be used to solve the single degree of freedom and two degree of freedom of honeycomb paperboard packaging system inner-resonance conditions. Make a certain analysis by considering the fatigue damage of inner-resonance conditions: single degree of freedom of honeycomb paperboard packaging system will appear inner-resonance at lower frequencies after fatigue damage. The equivalent elastic rigidity between the key parts and the product can be protected after the two degree of freedom of the honeycomb paperboard packaging system fatigue damage. The cumulative damage effect of the fatigue damage will effect on the two degree of freedom packaging system of honeycomb paperboard has large influence.