Abstract:

Selected mechanical parameters of earlywood and latewood from Pinus sylvestris subjected to tensile stress were measured as a function of moisture content. Microfibril angles (MFAs) to the longitudinal axis of the cell in the S2 layer of tangent cell walls in the same wood samples were also measured. The tensile strength and modulus of elasticity of earlywood were practically independent of its moisture content, while the same parameters of latewood significantly decreased as its moisture content increased in the hygroscopic range. For earlywood, the strain at break was greater the higher its moisture content. For latewood, no notable effect of moisture content on the strain at break was observed. The influence of moisture content on mechanical parameters measured upon tensile stress was proven to be determined by mean MFA values. This influence was the most pronounced for low MFA values, up to about 13°, while for mean MFAs from 13° to 22° the tensile strength and modulus of elasticity were practically constant and independent of moisture content.

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