Applying failure criteria to the strength evaluation of 3-ply laminated veneer lumber according to grain direction by uniaxial tension test

The failure criteria from four theories — the Hankinson formula, Maximum stress theory, Tsai–Hill theory and Hyperbolic formula (modified Hankinson formula) — were applied to estimate the strength of laminated veneer lumber (LVL) by uniaxial tension test at various angles to the grain. The LVL strength predicted from these theories were compared with actual data to evaluate the accuracy of the criteria. The tensile strength rapidly decreased at orientations between 0 and 15°. In the Hankinson formula, the difference between the predicted strength with n = 2 and the measured data was very small, with a slight underestimation at grain angles of 15°, 30° and 45°. The Maximum stress theory predicted the LVL strength better at grain angles over 45°, but not under 45°. The predicted strength derived by the Tsai–Hill theory underestimated the strength at grain angles of 15°, 30°, and 45°, with the difference being the largest at a grain angle of 15°. The prediction of LVL strength using this theory may be somewhat misleading in small grain angle deviations. The Hankinson and Hyperbolic formulae showed good strength prediction according to grain variation, especially at small grain angles. These two formulae are more useful/practical in the estimation of engineered wood composites like LVL according to grain direction deviation between veneers in the lay-up process. Among the failure types of the tested LVL specimens, the shear failure parallel to the grain was predominant at each grain angle except for 0°. This resembles the cross grain tension failure type, while splintering tension failure was found at 0° and brash tension-like brittle fracture at 90°.