Comparison of the in-plane shear strength of OSB and plywood using five point bending and EN 789 steel plate test methods

摘要

In order to assess the interlaminar shear strength of spruce plywood and oriented strand board (OSB) five point bending tests and shear tests according to EN 789 were performed. Additionally, a linear elastic finite element analysis of both test set-ups was performed to visualise the distribution of shear stresses. While shear stress was homogeneously distributed in EN 789 samples, typical s-shaped stress fields were observed in beam sections of five point bending specimens. Experiments showed a higher shear strength for plywood compared to OSB. In addition, apparent shear strength measured by five point bending was higher than values obtained using EN 789, the difference being significantly more pronounced for plywood (tau(5-pt)/tau(EN789) = 1.7) than for OSB (tau(5-pt)/tau(EN789) = 1.3). It is concluded that differences in the structure of OSB and plywood lead to a bias in the measured apparent shear strength of plywood by means of five point bending tests. Since apparent shear strength values determined by five point bending tests are, therefore, not only dependant on span to thickness ratio, but also on composite structure, EN 789 is recommended for interlaminar shear testing of wood composites.