The Optimizing Cybernetic Technology Of Vertical Density Profile Distribution Of Fiberboard And Its Prediction Model Of Mechanical Performance

As an important structure characteristic of fiberboard, Vertical Density Profile (VDP) has great impacts on the physical and mechanical performance of panel, which becomes a link between manufacturing technology and physical and mechanical performance. To study the relationship of manufacturing technology, VDP distribution and physical and mechanical performance of panel and establish the structural optimization and performance cybernetic system of fiberboard on the basis of VDP distribution, have significant meaning for optimizing manufacturing technology, improving integral property of panel, exerting material performance.Under the conditions of traditional hot pressing technology and "flat pretreatment-hot pressing" combination technology, the essay had researched on shape distinction, formation mechanics and quantitative model of VDP distribution of panel. Influence models of processing parameters on fiberboards'VDP distribution had been built. The processing technology of ideal isotrope fiberboard and U-shape VDP distribution fiberboard had been researched and developed, and the mechanical performances had been compared. Based on micro-analysis of fiber arraying feature of fiberboard, summing up sheet lamination theory, elasticity mechanics and theories for fiberboard property within intensity theories, section stress distribution model, bending failure mechanism and determining model of failure types, elasticity modulus and prediction model of MOR in the process of three-points bending loadTherefore, the main conclusions of the article are below:1. Thickness of procuring layer, ratio of surface density, density and thickness of sandwich layer can be used to quantify VDP distribution of panel, produced under the condition of traditional processing technology, the main impact factors for surface density and procuring layer thickness are moisture and high pressure, the main impact factors for density and thickness of sandwich layer are moisture and once reduction pressure. The optimizing panel production technology of "steep-flat" shape VDP distribution under the traditional technology can be obtained on the basis of comprehensive analysis. Panels produced by optimizing technology is qualified with expectation, however, the purpose of eliminating procuring layer and equalizing sandwich layer's density is still under research.2. Considering the parameters of mat moisture, pre-heating temperature, pre-heating time in mat pre-heating process, the prediction model of inner temperature can predict temperature variation of core layer during pre-heating. After pre-pressing, pre-heating, surface humidification and the combination technology of "mat pretreatment-hot pressing", relatively isotrope fiberboard and U-shape VDP distribution fiberboard can be obtained and the purpose of eliminating procuring layer and equalizing sandwich layer's density can be achieved basically. The VDP distribution of fiberboard produced by the combination technology of "mat procuring-hot pressing" can be quantified by density deviation of surface and core layers and thickness rate of unifonn core layer. According to prediction model of mat inner temperature in pre-heating process and relation model of shape factors of VDP distribution and core layer temperature after mat procuring, quantitative prediction model of VDP distribution can be established.3. Fiberboard can be regarded as cross isotropical, longitudinal anisotropical material, positive stress of any point at the thickness direction in panel bending process has relationship with section density inertia of panel, and there is no linear relation with the distance from neutral layer. Breakage of cracking and shear are the two basic bending failure types of fiberboard, containing the lowest density, highest density and bending failure type's determined factor K which is decided by section density inertia. Cracking failure occurs when K>1, shear failure occurs when K<1. Bending intensity not only has relationship with average density, highest density and lowest density of panel, but also with inertia intensively, which contribute to establish MOE built up by quantitative factor of panel VDP distribution and prediction model of MOR.