DEVELOPMENT OF COMPRESSED WOOD FASTENERS FOR TIMBER CONSTRUCTION .1. MECHANICAL-PROPERTIES OF PHENOLIC RESIN IMPREGNATED COMPRESSED LAMINATED VENEER LUMBER

To develop compressed wood fasteners for timber construction, rotary-c ut veneers of sugi (Cryptomeria japonica D. Don) were impregnated with low molecular weight phenolic resin (PF) and pressed into laminated v eneer lumber (LVL) of parallel laminates (P-type) or crossbanded lamin ates (C-type) by hot pressing. The mechanical properties for bending, compressive and horizontal shearing of the compressed LVL were determi ned. The results were as follows: 1) PF concentrations of about 15% wa s appropriate to obtain both great strength and dimensional stability. It was estimated that the mechanical properties of the P-type with a density of 1.3 g/cm(3) were 2-7 times as much as those of glued-lamina ted timbers of Douglas-fir (Pseudotsuga menziesii (Mirb.) France).2) T he mechanical properties of the C-type decreased with increasing numbe rs of crossband veneers, and those of crossbanded laminates, quite lik e the plywood, were about 70% of those of the P-type. The mechanical p roperties of the C-type having various laminated patterns could be cal culated on the basis of both those of the P-type and the positions of the crossband veneers. 3) The changes of the mechanical properties wit h changes of the grain angle of the compressed LVL could be calculated using a Hankinson-type formula. For the P-type the mechanical propert ies, except for the compressive strength, decreased considerably with increasing grain angle, but for the C-type no mechanical properties we re changed very much by changes in the grain angle, but they were grea ter than those of the P-type at grain angles of more than 30 degrees. 4) C-type had great horizontal shearing strength for edge-wise loads a nd a very ductile behavior at grain angles of more than 30 degrees. Th erefore, this type of compressed LVL is suitable for fasteners.