Effects of strain-rate on the transverse strength of Pinus radiata wood

Summary The effects of strain-rate, moisture content, and bulk density on the transverse fracture properties of Pinus radiata wood are described. As the strain-rate is increased from 2×10^-6 sec^-1 to 10² sec^-1, the strengths of both wet and airdry woods increase, with the greater increase occuring in wet wood. At the same time, the failure strain tends to decrease. The energy absorbed by airdry wood decreases, and that absorbed by wet wood increases. An explanation of the variation of strength with strain-rate is developed. Initially the measured strength of latewood is related to the strength of the compound middle lamella matrix connecting adjacent tracheids, and then by making the assumption that wood failure occurs when a certain proportion of the load bearing hydrogen bonds in the matrix have failed, and by applying reaction rate theory to the formation and rupture of the stressed hydrogen bonds, a strength versus time to failure relationship that is in good agreement with the experimental data is derived.The work described below was carried out at the Physics and Engineering Laboratory as part of a PhD research program at the Victoria University of Wellington.