Influence of layering arrangement and compression level on the characteristics of three-layered solid wood panels
Steiger, B.(Hochschule fuer Architektur, Bau und Holz, Biel (Switzerland)) | Niemz, P. | Hurst, A.
The level of compression and the arrangement of layers were varied on layered solid wood panels, produced in the laboratory using technical methods and glued with polyurethane (PUR). Measurements were subsequently carried out on the E-module, bending strength, diffusion resistance level, changes in length caused by changes ambient climate, as well as the warping in a fluctuating climate. Following results were recorded. The level of compression with the PUR glue used in the experiment had no influence on the tensile strength or the E-module. When the proportion of middle layer wood is increased in the panel, the tensile strength of the covering layer falls when stressed parallel to the direction of the fibre. It rises when the covering layer lies at a right angle to the direction of the fibre. The quality of the panel can be influenced by varying the quality of the wood used in the covering and middle layers, e.g. by sorting. Slitting the middle layer leads to a clear reduction of shearing strength (rolling shear) when the panel is stressed, and the covering layer is parallel to the longitudinal axis of the sample. On the other hand, with the longitudinal axis lies at right angles to the covering layer (stressing of the middle layer parallel to the fibre), the influence of slitting is slight because the weakening of the cross-section is considerably less. Warping in a fluctuating climate can be clearly improved with rift cut in the covering layer. Diffusion resistance only continues to increase between pressures of 1 to 2 bars, and subsequently remains constant. Differential longitudinal swelling is influenced by the arrangement in construction.
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