Research On Mechanical Properties Of Honeycomb Sandwich Composite Material

Honeycomb sandwich composite material is made of honeycomb core,fiber and resin.Because the honeycomb is made up of equilateral polygonal,when apply the load perpendicular to the plate surface,the bending stiffness is comparable with that of the solid plate of the same thickness and the same material,and the weight can be reduced by60%-90%.However,this feature also causes the honeycomb sandwich composite material not firmly cemented during the forming process,resulting in problems such as cracking between panel and core during use.Therefore,by researching in the parameters of honeycomb sandwich panels and designing Nomex honeycomb cores and panel laminates for honeycomb sandwich panels,the purpose of this paper is to improve the performance of Nomex honeycomb and panels and to solve the above application problems.The main research contents are as follows:(1)The effects of molding process of honeycomb sandwich composite material on its flatwise compression,bending and impact properties were studied by orthogonal tests.The data of honeycomb sandwich panel was analyzed by grey relational analysis,and the results showed that the influence of molding pressure on the performance of honeycomb sandwich panel is less.The molding time has a great influence on the Young's modulus and bending properties.The forming temperature has a significant influence on the collapse stress and impact property in the flatwise compression tests of honeycomb.The optimized honeycomb sandwich panel forming parameters were obtained by data analysis.Comparing the mechanical properties of the honeycomb sandwich panel with the commercial honeycomb sandwich panel,it was found that the self-made honeycomb sandwich panel has strong flatwise compression,bending and impact strength.Using scanning electron microscope to observe fracture morphology of the honeycomb panel,and the results showed that the crackof the optimized honeycomb sandwich panel extend along the interface and the fiber appeared to be less,and the fracture is flat,which explains the destroying way of the honeycomb panel from the interface perspective and puts forward to improvement measures.(2)In this paper,the effects of honeycomb size and length-width ratio on the out-of-plane properties of Nomex honeycombs were studied by tests and simulations.On the one hand,as the size of the honeycomb increases,the collapse stress rises gradually,and the Young's modulus decreases gradually,and the change trend gradually becomes gentle,while it's less effect on the platform stress and the compacted strain during the flat pressing stage.On the other hand,with the increase of the length-width ratio of the honeycomb panel,collapse stress and Young's modulus of the honeycomb are gradually decline,at the same time the platform stress and densification strain of the honeycomb are basically unchanged.The test results was consistent with the finite element simulation results.Moreover,by observing the stress contour through the simulation results,it was found that when the honeycomb is flatwise compression test,the corner Nomex cells priority failure.(3)The effects of honeycomb sandwich composite panel's layer and angle on its bending and impact properties were studied by finite element simulation.The bending performance of honeycomb sandwich panels with thickness of 2,4,6,and 8 layers was calculated.It was found that the greater the thickness of the laminate,the greater the bending ability of the honeycomb sandwich panel.However,when the number of layups exceed 6layers,the increase in the bending strength of the honeycomb core gradually becomes gentle,which leads to an increase in the cost of the honeycomb sandwich panel.Then,based on the thickness of 6 layers,the simulation of the panel layup angle was continued.It was found that the panel layup angle has little effect on the bending performance of the honeycomb sandwich panel.After that,the impact performance was analyzed,and the number of layers was also changed.It was concluded that the impact strength of the honeycomb sandwich panel increased linearly with the number of layers.The stress contour of the honeycomb sandwich panel showed that during the bending process,the upper panel of the honeycombsandwich panel is stressed and the lower panel is less stressed.During the impact process,the impact of the panel layup angle on the impact performance is significant.Through the above research results,it has guiding and reference significance for the preparation and design of honeycomb sandwich panels.According to actual needs,suitable honeycomb sandwich composite materials can be designed to meet the requirements of mechanical properties and reduce costs.