Studies On The Mechanical Properties Of Graded Moso Bamboo Curtain Composite

Though the great variation of the physical and mechanical properties of the Moso bamboo (Phyllostachys pubescens Mazel) is known, the bamboo strips are mixed together in manufacturing the bamboo strip composite in many bamboo factories. Mixing method is convenient but hard to accomplish the optimization use of the bamboo material. The major purpose of this research is to accomplish the optimization use of the bamboo material through bamboo strip grading and scientifically designing of the bamboo curtain composite. The following jobs have been done in order to realize this purpose: testing and analyzing the physical and mechanical properties of bamboo material at different location, and seeking for reasonable bamboo strip (bamboo curtain) grading rules; testing and analyzing some mechanical properties of parallel Moso bamboo curtain laminated panels; simulating the bamboo curtain composite to predict the MOE.The basic properties (including basic and air-dried density, the shrinkage rate, the tensile strength and the tensile modulus of elasticity parallel to grain) of Moso bamboo at different locations were studied. The results show that the tensile modulus of elasticity parallel to grain declined most rapidly form the outer to the inner part of the bamboo wall, that compared with the softwood the tensile strength of inner and outer part of bamboo is higher, and the tensile modulus of elasticity parallel to grain of inner part is lower. So it is suitable to grade the bamboo strips according to the tensile modulus of elasticity parallel to grain. For the craft of cutting the bamboo wall into 6 strips with the same thickness, the grading system of 4. 3 and 2 grades are established respectively.The parallel bamboo curtain laminated panels of different grades were manufactured in the laboratory using the mature production technology of bamboo curtain plywood, and the bending and compression properties have been studied respectively. The results show that the properties of different grades of parallel bamboo curtain panels differ greatly: the MOE of the highest grade laminated panel is about the 3 times that of the minimum grade; the bendingstrength, the proportional limit of bending, the compressive strength parallel to grain of the highest grade laminated panel are approximately 2 times those of the minimum grade. The gap in the mechanical properties (especially MOE) of different grades of parallel bamboo curtain laminated panel is big. Therefore, the construction of bamboo strip grading system is necessary and helpful for bamboo utilization properly and efficiently.The accelerated ageing tests of the parallel bamboo curtain laminated panels of grade I ,III and IV 2 were carried out in accordance to ASTM D1037-96a. The test results indicated that the ageing resistance of the panel manufactured with the bamboo strips of grade I (with a little bamboo epidermis which wettability is bad) and panels manufactured with the bamboo strips of grade IV2 (with a little bamboo pith which wettability is bad) is not bad.The bending creep factor of the parallel bamboo curtain laminated panels of grade II and IV 1 were studied in accordance to ENV1156. The main conclusion is as the following: bamboo panels absorbed and desorbed moisture slowly; there is little difference in creep factor between the two grades of parallel bamboo curtain laminated panels (MC: 5-7%)at a stress level of 21% Fmax. In addition, power law functions can well define the relation between the creep factor and the creep time.Compared with wood as well as some structural composite lumber, the MOE and MOR and compression strength of the high-grade parallel curtain laminated panel is higher; the strength of the low-grade panels is medium but the MOE is lower. How to use the low-grade bamboo strips reasonably is a problem to be solved. If the structure of the bamboo curtain composite was designed scientifically and each grade of the bamboo strips was used efficiently, the quality of the product would be promoted. With Monte-carlo technology, the bending theory of the bea...