Study On The Physical And Chemical Properties Of Interface Of Moso Bamboo/Chinese Fir Composite

Wood-based-panel is played an important role in the world wood industry. As a long term, China has been occupying the largest production of wood-based-panel country of the world. Accroding to the unique resourse situation of China, bamboo/wood composite materials have taken the advantage in the international mark. The properties of bamboo/wood composite plywood, as a main production of wood-based-panel, were studied in this dissertation.In the experiment, Moso bamboo (Phyllostachys pubescens Mazel ex H.de Lebaie) and Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) were adhesived by phenolic resin.The purpose of this dissertation was to reserch the relationship between the properties of composite units-which were included the surface roughness of Moso bamboo/Chinese fir , the contact angle, permeability coefficient-and the adhesive parameters-such as the bond strength, adhesives permeability, layer thickness, interface stress and strain distribution, the interface damage displacement and time of Moso bamboo. In order to establishing the relation The morphology of the bonding interface was observed by environmental scanning electron microscope(ESEM) and chemical functional groups changes were measured through fourier transform infrared(FTIR). Research methods and results were as follows:1) The surface roughness of Moso bamboo and Chinese fir veneer on different wetting properties was measured by contact angle analyzer instrument. The results shows: there were significant influences on the adhesive parameters (the initial contact angle, equilibrium contact angle, permeability coefficient of the phenolic resin adhesive) by types of the materials and the sanding treatments. Therefore, sanding treatment improves the property of surface-wetting of both Moso bamboo and Chinese fir.2) The surface roughness of sanded Moso bamboo and Chinese fir were scaled by two-dimensional contours of roughness and laser confocal three-dimensional shape measuring instrument. The results shows that: the three kinds of parameters about surface roughness including profile arithmetic average error(Ra), ten point height of irregularities(Rz), and maximum height of profile(Ry), were changed significantly on both Moso bamboo and Chinese fir. Comparing with the parallel to grain, the numerical value of surface roughness on the perpendicular to grain was larger. The outer circle of Moso bamboo surface roughness was greater than inner skin. Besides, the tight side of Chinese fir veneer surface roughness was higher than loose side. Laser confocal instrument was a better method which is able to directly obtain perfect two-dimensional roughness contour lines and the three-dimensional space.3) The bond interface of Moso bamboo, Chinese fir and Moso bamboo/Chinese fir of composite materials were studied by environmental scanning electron microscope and electron microscope. The results show that: wood tracheids radiation were open on the tight surface of fir veneer and some wood tracheids were closed on loose side of Chinese fir veneer. There was no difference between outer circle of Moso bamboo and inner skin. The interface layer thickness of Chinese fir was larger than Moso bamboo. There was adhesive infiltration into the surface of parenchyma cells and ray tracheids using scanning electron microscopy surface energy spectrum was able to be located. There were phenomenon that the fir veneer surface of tracheids, parenchyma cell surface and bamboo fiber had been torn or pulled off in interface fracture.4) Bonding interface and the layer thickness of adhesive permeability were studied by fluorescence microscopy. The results indicate that: it was significantly effected on the interface permeability and layer thickness by different surface treatments. Through the comparison studied of cross section and radial section found, there was little difference of layer thickness on the two facets. However, the effective penetration of significant differences and radial section results were larger than that measured by cross-section.5) Bonding performance of different lay up and different surface roughness of Moso bamboo, Chinese fir, Moso bamboo/Chinese fir of composite materials were studied. The results indicate that: different lay-up and different surface treatment affected on wet and dry bonding strength significantly. The bonding strength of outer circle of Moso bamboo was the largest, following by bonding strength of inner skin of Bamboo.The bonding strength of tight side of Chinese fir veneer was larger than the loose side. And the bonding strength of Moso bamboo/Chinese fir of composite materials was between Moso bamboo and Chinese fir.6) The test methods by digital speckle correlation method on strain of Moso bamboo, Chinese fir, Moso bamboo/Chinese fir of composite materials under different loading conditions, different lay up, as well as horizontal and vertical maximum displacement and time relationships were studies. The results show that: with the increase in load force, the strain gradually increased and the increase in the initial segment strain faster. When the force reaches a certain value, the strain increased trend steady. The maximum shear strain of bonding interface in the layer ends, different lay up have quite different strain and destroyed time. Different lay up and different surface roughness affected the layer destruction of displacement and times significantly.Vertical displacement curves was rough, but lateral displacement smooth relatively.7) The interface of Moso bamboo, Chinese fir of chemical functional groups changes before and after was studied by infrared spectroscopy. The results show that the functional groups of Maso bamboo and Chinese fir which had a subtle change before and after hot pressing. However, some functional groups of adhesive layer had changed.