Influence of compression wood on strength and elasticity of spruce timber
1999
Seeling, U.
German. Non-destructive evaluation methods are getting more and more important in the wood processing industry to predict the strength of the material. At the same time the customers are afraid they will get in the future roundwood with different characteristics (more and bigger knots, higher percentage of reaction wood) compared to the actual material because the forest enterprises have changed their silvicultural strategies. These current developments gave the motivation to analyse the consequences of compression wood for the accuracy of non-destructive testing by the natural frequency-method. For this research more than 500 samples of spruce with the dimensions 20 x 20 x 360 mm were sawn - one part defectfree samples according to the German norm DIN 52 180, the other part samples with compression wood. At an average moisture content of 12% the parameters density, dynamic and static modulus of elasticity and bending strength have been measured. For the defectfree samples strong correlations were found between bending strength, dynamic and static E-modulus as well as density. The occurence of compression wood weakened the correlations so that none of the E-moduls were suitable to predict the bending strength.
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