Structural Composite Boards Made from Wood Fiber and Domestic Plantation Conifer Wood

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This Research deals with the mechanical and physical properties of composite boards made with soft wood fiber and two types of Sugi particle (shaving and strand) in order to develope high performance wood based boards.Firstly, the effect of mixing ratio of wood fiber and two types of particle on the properties of homogeneous boards were evaluated. Modulus of elasticity of homogeneous boards increased with increasing mixing ratio of particle to fiber, especially at fiber-strand boards. However, no significant differences were found among the bending strengths for fiber board, fiber-shaving board, fiber-strand board and the mixed boards. Bending property retention increased with increasing mixing ratio of wood particle. On the contrary, there was no consistent differences in internal bond strength among boads.Three-layr boards that consisted of fiber elements as face layrs and particle elements (shaving or strand) as a core layr showed remarkably higher bending properties compared with t … More hose of the three-layr board hving the inverse element construction. This was due to the formation of high density surface layrs during hot pressing when fiber was used un the face layrs.Next, flexural creep behavior of ten laboratory composite boards made with soft wood fiber and Sugi particles was evaluated under natural interior climate. In this study, three replicates of each board were used at each stress level. Stress level ; 10,20,30,40%, Loading time ; max.290h, Test term ; May 10-Aug.10 in 1994.As for relative creep of homogeneous boards made with wood fiber and particle, relative creep increased with increaing mixing ratio of particle to fiber, and especially at fiber-stand board. This is because large flakes with their large contact areas provide sufficient horizontal shear strength between particles.Three-layr boards consisted of particle elements (shaving or strand) as face layrs and fiber element as a core layr showed remarkably lower relative creep than MDF and the three-layr board having the inverse element construction. This is completely oposite construction to short-term bending property.As for the effect of stress lebel on the creep behavior, which was measured on the three kinds of composite boards made with the same materials (50 percent fiber and 50 percent shaving), the three-layr board made with fiber for the surfaces had a tendency to increase in relative creep more sharply than the other two boads with an increasing stress level.The strongest correlation was observed between the relative creep and the bending properties ratio (MOE/MOR) of tested composite boards. Then it appered to esttimate the relative creep of composite boards from their bending properties ratios. Less