Preparation And Mechanical Properties Of Hollow Spherical Shell Filled Honeycomb Sandwich Composite Materials

Honeycomb sandwich composites are widely used in aerospace,land vehicles and ships due to their advantages of light weight,high strength and strong designability.With the continuous application of large volume,high weight and high energy consumption equipment in various fields,a single honeycomb sandwich material is difficult to meet the existing engineering design requirements,so it is necessary to develop the combined honeycomb sandwich composite material with light weight,higher strength and stronger energy absorption.The overall carrying capacity and energy absorption capacity of honeycomb sandwich composites can be significantly improved by filling hollow spherical shells into the honeycomb core.In this paper,carbon fiber panels are prepared by using different post-curing pressure,temperature,time molding processes,and the tensile,bending,shear properties are tested respectively to explore the best molding processes.The results showe that:in the process of gradient temperature rise and gradient pressure,the pre-curing is 90℃,2.5 MPa,30 min;After curing for 130℃,5 MPa and 90 min,the mechanical properties of the carbon fiber panel are the best,and the tensile,bending and shear strengths are 811 MPa,1242 MPa and 68 MPa,respectively.The mold curing system of the carbon fiber panel is selected with this parameter.Carbon fiber panels with optimum process forming parameters are selected as raw materials.The L and W direction honeycomb sandwich composites with densities of 0.39g/cm³,0.42g/cm³,0.46g/cm³,0.49g/cm³,0.55g/cm³,which are not filled hollow shell and filled hollow shell are prepared by molding.The results show that the density of honeycomb sandwich composites increases with the increase of the density of hollow shell.The honeycomb sandwich composite with hollow shell density of 0.46 g/cm³ has the best shear and bending properties.The shear strength and bending stiffness in the L direction are 1.25 MPa and 13.94 N/m²,and the shear strength and bending stiffness in the W direction are 0.96 MPa and 11.33 N/m²,respectively.The flexural and shear damage mechanisms of honeycomb sandwich composites filled with hollow spherical shells are analyzed.The shear damage mechanisms can be divided into three stages:elastic deformation stage,failure stage and tearing stage.The bending damage mechanism can be divided into four stages:elastic deformation stage,crushing stage,crushing stage and densification stage.The flat compression,side compression and Hopkinson bar（SHPB）dynamic compression tests are carried out for honeycomb sandwich composites filled with hollow spherical shells.It is found that under flat compression load,when the density of the filled hollow spherical shell is 0.46 g/cm³,the honeycomb sandwich composite material has the best comprehensive strength and energy absorption performance,with 7.09 MPa·cm³/g and 764 J/kg,respectively.The flat compression damage mechanism can be divided into three stages:elastic deformation stage,stacking stage and compaction stage.Under side compression load,honeycomb sandwich composite with hollow shell density of 0.46 g/cm³ has the best comprehensive performance,and its specific strength and specific energy absorption in L direction are 91.84 MPa·cm³/g and1422 J/kg,respectively.W direction specific strength and specific energy absorption are 79.76MPa·cm³/g and 1115 J/kg,respectively.The lateral compression damage mechanism can be divided into four stages:elastic deformation stage,wrinkle stage,fatigue stage and failure stage.Under the dynamic compression load at 1900 s^-1,the honeycomb sandwich composite with hollow shell density of 0.46 g/cm³ is filled with the maximum specific energy absorption of184.21 m J/kg.