Effect of Wood Specimen Length on Uniaxial Stress–Strain Curve along the Grain Direction

Abstract The axial compression test was carried out on the basis of three different-size specimens of white wax (Fraxinus chinensis), fir (Abies fabri), and Yunnan pine (Pinus yunnanensis) to explore the influence of specimen length on the compression strength parallel to grain, peak strain, and elastic modulus of wood. Weibull’s weakest-link theory, Bazant’s law of size effect, and Carpinteri’s multiple fractal size effect were used for the analysis. The results showed significant size effects on theses parameters of wood along the grain. Using the three theories to predict the compressive strength of 100-mm-length specimens, the predicted value of Bazant’s law of size effect has the smallest error with the measured value, followed by Weibull’s weakest-link theory and Carpinteri’s law of multiple fractal size effect. The size-effect coefficients of the down-grain compressive strength of the three woods obtained using the slope method were 0.06, 0.11, and 0.09, respectively, which were consistent with the values of m in the Weibull fitting function.