Developing hybrid wood-based panels for resources recycling

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The aim of this research project was to develop new type wood based panels which could be regarded as resource recycling and environmentally friendly. Laboratory size and full size panels were produced experimentally, and the technologies to be newly developed were discussed. There are two big issues concerning wood resources in Japan. One is conifers planted widely in Japan, and the other is waste wood generated from demolition_ The third item was a plantation species imported form foreign countries, that is, Eucalyptus grandis which can be used to plywood by peeling. Using these wood resources, The 'hybrid' wood based panel was discussed.Three layer strandboard with sugi-strand for face layers and with recycled wood particle for core layer was fabricated. It was revealed that this type of panel had enough strength compared with panels for structural purpose. When the strands in the face layers had orientation, mechanical properties in the aligned direction were enhanced remarkably. In addition to these strand board with/without alignment, five-layer structured boards were fabricated to determine the effects of layer thickness. The board consisted of two strand layers cross oriented each other, a recycled particle layer as a core layer, and two strand layers as the back. It was found that orientation and thickness of the outer was more effective to the mechanical properties, and that the elastic constants could be predicted by those of uni-layer board. Using thinner strand was proved to be effective for dimensional stability in thickness direction. Also a hybrid-plywood having of combinations of sugi- and Eucalyptus-veneer, were fabricated. Eucalyptus veneer used in the face ply gave very high elastic and strength properties to the plywood. The plywood using sugi-veneer in the face had the preference because of favorable face appearance of the texture, while the mechanical properties became lower.