Effects Of Particle Geometry And Layer Structure On The Properties Of Oriented Structural Straw Board(OSSB)

The objectives of this research were to evaluate the mechanical and physical properties ofwheat straw boards made with various types of particles and layer structures. Specifically, thewheat straw boards were fabricated in a laboratory at diverse sizes of particles processed bysplitter and flaker. The influence of various degree of splitting was investigated as well. Interms of layer structures, the effect of three different structures (randomly orientedhomogenous board, unidirectionally oriented homogenous board and a three-layered boardwith a cross-oriented core layer) on the performance of OSSB was disscussed. In addition, theinfluence of various face-to-core ratios on the properties of OSSB was investigated. Resultsobtained can be summarized as follows.(1)Compared with boards made from particles processed by flaker, the higher MOR, MOE,WA and TS and the lower IB were achieved by using strands processed by splitter. Anincrease in the dimension of particle affected the physical and mechanical properties of thepanels produced. The MOR, MOE,24h TS and24h WA of boards showed an upward trendwith increased particle size, whilst IB decreased with increasing particle size.(2)Straw strand alignment distribution and bending properties increased with the decrease inthe percentage of split straw. With the increase in the proportion of unsplit straw, the MOR ofthe three layered board in the parallel direction increased remarkably; in the perpendiculardirection, it exhibited no difference. However, IB dropped to0.31Mpa when the proportion ofunsplit straw was50%.2h,2h TS and24h TS were greatly affected by the degree of splitting,but it did not appear in24h WA. IB declined substantially while the proportion dipped to50%.This study revealed that mechanical and physical properties of such experimental panels wereinfluenced by the the degree of splitting.(3)Bending properties were affected by layer structures. The MOR of the three layered boardin the parallel direction increased remarkably compared with the random board MOR; in theperpendicular direction, it exhibited less strength reduction. IB was not affected by the layerstructure. Comparison of MORs of boards manufactured from particles processed by flaker,revealed that in unidirectionally oriented homogenous board, the MOR in the orienteddirection was1.7times that in the perpendicular direction, and was1.3times that in randomly oriented homogenous board. These values were higher than those of OSSB made fromparticles processed by flaker. The MOR in the perpendicular direction was1.2times that inthe cross-oriented direction, and equalled that in randomly oriented homogenous board.Comparison of MORs in OSSB and randomly oriented homogenous board revealed that athree-layer structure provided higher MOR in the parallel direction with less strengthreduction in the perpendicular direction. A similar trend in boards made from strandsprocessed by straw spliter was observed in MOR and MOE. The MOE for unidirectionallyoriented homogenous board in the parallel direction was3.2and1.5times, respectively, tothose for the perpendicular direction of unidirectionally oriented homogenous board andrandomly oriented homogenous board. Some differences in24h TS appeared between boardtypes; OSSB manufactured from particles processed by flaker exhibited smaller24h TS thanboards made from strands processed by spliter. In terms of boards made from particles andstrands, there was no significant difference found for the IB between three types of structures.However, IB of boards made from particles was higher than strands. It was obvious that MORand MOE in a parallel direction increased with an increase in the face-to-core ratio; and theMOE in the perpendicular direction decreased with the face-to-core ratio. However, bendingproperties experienced a opposite trend while the ratio was1:8:1.