Design,Preparation And Mechanical Performance Of BFRP Sandwich Insulation Panels

After more than seventy years development,traditional light steel and wooden structure mobile houses has been widely used.However,due to the material characteristics,the mobile houses are always facing with the problems of poor corrosion resistance,low thermal insulation performance and poor fire performance,etc.so its application in the coastal environment of strong corrosion and cold areas on the plateau is greatly limited.The development of mobile houses has an urgent need for the use of new lightweight and high-strength materials.Basalt fiber reinforced polymer material(BFRP)has the characteristics of lightweight,high-strength,corrosion-resistance,etc.So it is the ideal material to build assembled lightweight activity rooms instead of conventional materials like steel and wood.Performance parameters of FRP structure mobile houses are mainly determined by the envelope system,different characteristics of BFRP sheets combined with thermal insulation core material can obtain high bearing capacity,good corrosion resistance and good thermal insulation palisade structure panel system,which provides a new train of thought to solve the problem of traditional material structure housing.According to the above research background,this thesis takes BFRP composite sandwich insulation panel of the mobile house envelope system as the center,and systematically studies its design,preparation methods,flexural mechanical properties and finite element numerical simulation.The details are stated as follows.(1)Material selection,design and preparation of the BFRP composite sandwich panels.By introducing the vacuum bag molding techniques,BFRP sandwich panels are made by hand with basalt fiber chopped strand mats and basalt fiber 0°/90° symmetric woven fabric mats,and its mechanical performance test results show that the FRP plate prepared mainly with basalt fiber chopped strand mats composite symmetric woven fabric mats can meet the mechanical requirements of composite sandwich panel without local shear failure;Polyurethane rigid foam(PU),extruded polystyrene foam(XPS)and rock wool are used as the thermal insulation core,which results of material performance test indicate that mechanical properties of different materials vary greatly,and the influence of material density and fiber distribution direction should not be ignored;The theoretical formula considering the contribution of shear deformation of core material to the deflection of composite sandwich structure are derived,Finally,three different kinds of BFRP laminate plates are optimized for subsequent tests.(2)Experimental study on the bending mechanical properties of BFRP composite sandwich panels.Different test groups of composite sandwich panels can be prepared by combining four kinds of general density polyurethane core material thickness between 30 mm ～ 100 mm,50 mm thick high-density polyurethane core material,extruded polystyrene core material and rock wool with three different layer BFRP faces and 0.5 mm thick galvanized steel plate,and then 3-point bending load,4-point bending load and uniform load simulated by 6-point bending load are applied to test its bending mechanical properties.The results show that the design of the composite sandwich structure component is controlled by stiffness deformation,the overall quality control effect of the composite sandwich panel made by hand is well.By increasing the thickness and density of core material,changing the type of surface layer BFRP faces and core material can improve the overall bearing capacity of composite sandwich panel in different degrees,so that the bearing capacity results can meet the design requirements of mobile house envelope structure,and generally have a safety reserve factor much higher than that of reinforced concrete structure.However,the contribution of the shear deformation of the core material to the overall deformation cannot be ignored,and different loading modes have a great impact on the failure mode and bearing capacity of the composite sandwich structure.The combination of rock wool and hard foam material can also obtain the composite sandwich plate with non-single core material,which has the function of heat preservation and sound insulation as well as high bearing capacity,which has a broad application prospect.(3)Finite element simulation and comparative analysis of BFRP composite sandwich structure.The finite element simplified simulation can be carried on when using the ABAQUS skin command and shell elements to represent the structural surface layer: The stress cloud diagram and symbol variable diagram clearly show the distribution characteristics of shear stress of inner core materials,which is in good agreement with 45° shear failure mode of core material;Whether core material,skin or loading mode changes,the finite element bearing capacity results can be well consistent with the test results,and the deviation is controlled within 20%.Numerical analysis method can be good at simulating the BFRP composite sandwich structure as an alternative to theoretical formulas especially when the core is combined with different materials or irregular load is applied on it.The finite element method provides convenient and quick solutions,at the same time helps designers with inspiration and support for optimal design to understand the mechanical characteristics of composite sandwich structures.(4)Modification and application of theoretical formula of compound sandwich structure.The shear distribution coefficient of the core β(the percentage of the shear undertaken by the core material in the total shear)is introduced to modify the theoretical formula of composite sandwich structure,then the bearing capacity calculation formula is used to approximate the test results and the finite element results,the maximum deviation is only about 15%,and the overall deviation is mostly controlled within 6%.Summarizing the corresponding shear distribution coefficient β when the composition changes including surface skin and cores,combined with the modified theoretical calculation formula,the table of flexural capacity of composite sandwich panel with different core materials and skins can be deduced.It can be used easily for designers to refer and make a quick choice from extensive parameters.