Predicting strength of Finnish birch veneers based on three different failure criteria

The use of wood in high-performance composites based on laminated veneer products, plywood or wood hybrid elements thereof requires accurate prediction of strength of each individual ply. Previous research has shown that one dominating factor influencing the strength of birch veneers is the fibre orientation. The present study investigates the validity of the failure criteria after Tsai-Hill, Hoffmann and Kollmann for thin birch veneers under tensile loading. The fibre orientation in- and out-of-plane was measured by means of wide-angle X-ray scattering. Tensile strength and threshold values were determined in laboratory experiments. Pearson correlation between the predicted strength and actual strength ranged from 0.836 up to 0.883. Best correlation (r = 0.883) was achieved for Kollmann using a combined angle between in- and out-of-plane fibre orientation. It was shown that the failure criteria commonly used for manmade fibre reinforced composites are also applicable for thin birch veneers.