This document explains and demonstrates a new means of dynamic and static bending evaluation of modulus of elasticity for small samples of thin wood composites. This means is based on the principle of cantilever-beam bending and free vibration, and a cantilever beam testing apparatus has been developed according to this principle. Three kinds of thin particleboard obtained from market were processed and tested. The testing results show that there are significant linear correlations between the cantilever dynamic modulus and the static bending modulus. Through this method, it is feasible to measure the modulus of elasticity for thin wood composites, and compared with traditional method, the static bending test; it can save more time and reduce damage.
During maintenance of ancient timber architectures, it is important to determine mechanical properties of the wood component materials non-destructively and effectively, so that degraded members may be replaced or repaired to avoid structural failure. Experimental materials are four larch (Larix principis-rupprechtii Mayr.) components, which were taken down from the drum-tower of Zhengjue Temple of Yuanmingyuan (Old Summer Palace), Beijing, China. The larch components were cut into standard specimens first, and then stress wave transmission times, resistograph and densities were tested. Product of resitograph and stress wave speed squared is defined as modulus of stress-resistograph. Comparing with the modulus of elasticity (MOE) of the specimens tested by the traditional bending test method, it is found that there is a linear relationships between the modulus of stress-resistograph and modulus of elasticity (MOE), and the correlation coefficients are 0.7111. In order to better evaluate the modulus of elasticity (MOE) with the modulus of stress-resistograph, 95% confidence regression lines are suggested to be used for the future calculation.
To determine modulus of elasticity (MOE) of the whole full-sized medium density fiberboard (MDF) by using vibration method in the future, this paper studies MDF vibration characteristics. To solve modal parameters of full-sized MDF in the condition of free vibration, the writers conducted calculation modal analysis and experimental modal analysis of the full-sized MDF with three different thicknesses respectively, compared and analyzed the first three order modal shapes and frequencies. It is found that the full-sized MDF with three different thicknesses showed the same vibration modal forms: the first and second vibration modes had bending vibration along the length direction, while the third one had bending vibration along the width direction; the frequency obtained through calculation modal analysis and experimental modal analysis had a certain difference—the first calculation modal frequency was slightly lower than the first experimental modal frequency, and the second and third calculation modal frequencies higher than the corresponding experimental modal frequencies. However, there is a good correlation between calculation modal frequency and test experimental modal frequency with the determination coefficient reaching 0.9816.
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