Development Of Three-dimensional Woven Spacer Fabric Reinforced Epoxy Foam Sandwich Panel

With the development of the shipbuilding industry,marine plates not only need to meet higher mechanical properties,but their lightweight,non-magnetization,noise reduction and shock absorption are also important development directions.The foam sandwich structure composite material has the advantages of light weight,high strength,low moisture absorption,corrosion resistance,sound absorption,heat insulation,etc.,and has begun to enter the shipbuilding industry widely.However,most of the foam sandwich panels have the disadvantage of delamination after impact,which seriously affects their service performance.Therefore,this paper attempts to develop a new type of foam sandwich panel for ships with excellent overall performance by filling epoxy foam into the integrated three-dimensional woven spacer fabric.Firstly,this paper explored the influence of different foaming temperatures(85℃,95℃,105℃,115℃)and different foaming agent content(2%,3%,4%,5%)on the foam molding of epoxy foam,respectively.Combining the three indicators of foam density,cell shape and compressive strength to determine the most suitable foaming preparation system for the composite material.The research results show that when the foaming temperature is 105℃,the foaming agent content is 3%,and the density of the foam is 0.36g/cm~3,the compressive strength can reach 6.28MPa.Compared with other formulas,the pores in the SEM image show a full spherical shape with a relatively uniform size and distribution.Thereafter,three-dimensional woven spacer fabric,three-dimensional woven spacer fabric/epoxy resin hollow composite material(3DWSHC)and three-dimensional woven spacer fabric reinforced foam sandwich panel(3DWSRFP)were prepared.The SEM image of the cross section of the 3DWSRFP shows that the foam pores were finely and uniformly distributed in the material,with a good interface adhesion between the foam wall and the hollow composite skeleton.Secondly,the bending performance tests were conducted and the corresponding failure modes were analyzed of 3DWSHC,3DWSRFP and commercial marine panel on the warp and weft direction respectively to evaluated the application potential of 3DWSRFP through mutual comparison.The results show that compared to the 3DWSHC,the bending stiffness of the3DWSRFP is generally improved.In the warp direction,it increased from 1.04×10~7 N·mm~2 to1.48×10~7 N·mm~2 with an increasement of 45.41%.The weft direction increased from 1.36×10~7N·mm~2 to 1.89×10~7 N·mm~2,with an increasement of 39.96%.For commercial marine panel,after being damaged by bending,the material will directly delaminate and fail.While after the 3DWSRFP reaches the peak load,a platform will appear on the load-deflection curve,showing a certain degree of toughness and strength.Thirdly,this paper further tested the compression performance of 3DWSHC,3DWSRFP and commercial marine panel,and analyzed their damage modes.According to the experimental data,compared to the 3DWSHC,the compressive strength of the 3DWSRFP increased from 8.35MPa to34.09MPa,with an increasement of 308.26%.In addition,the lateral compressive strength in the warp direction also increased from 10.50MPa to 24.90MPa with an increasement of 137.14%.The lateral compressive strength in the weft direction has been increased from 15.93MPa to 30.05MPa,an increase of 88.64%.The lateral compressive failure diagram of the 3DWSRFP shows that the panel undergoes slow and uniform extrusion,the bending deformation without delamination failure;It can be seen from the lateral compressive stress-strain curve that the load does not drop sharply after reaching the maximum carrying capacity,but presents a ductile platform with high energy absorption characteristics.However,after the ocean plate reaches the maximum load,the bearing capacity decreases rapidly,and obvious layered failures can be observed in the failure pattern diagram.Finally,this article explores the impact response and failure modes of 3DWSHCs,3DWSRFPs and commercial marine panels at 10J,20J,30J,and 40J energy levels.The samples after 10J,20J,and 30J energy impact were respectively subjected to lateral compressive tests to evaluate the residual strength of the material.The research results show that the impact load(4000-5000N)of3DWSRFPs at different energy levels is higher than that of commercial marine panels(3000-4200N).After 40J energy impact,the impact surface of the 3DWSRFP has only a small area of depression,and the cracks on the back extend in the latitude direction in a"line"shape;while the commercial ocean panel has almost penetrating impact depressions,accompanied by interlayer delamination and board surface fracture.After 30J energy impact,the lateral pressure residual strength loss rate of the 3DWSRFP is only 22.29%,which is much lower than the commercial marine board(46.99%).The lateral compressive strength of the 3DWSRFP can still be maintained between 24-27MPa with a relatively long platform of resilience.