Effects of Component Ratio of the Face and Core Laminae on Static Bending Strength Performance of Three-Ply Cross-Laminated Wood Panels Made With Sugi (<i>Cryptomeria Japonica</i>)
Keywords:
Anisotropy, annual ring angle, cross-laminated wood panels, modulus of elasticity, shear forceAbstract
In order to improve the bending strength performance of three-ply laminated wood panels and use them as construction-grade panel materials, twelve types of three-ply cross-laminated wood panels whose percentages of core lamina thickness versus total lamina thickness were 33%, 50%, and 80% were made with sugi (Japanese cedar), and the effect of component ratio of the face and core laminae on their static bending strength performance was investigated.
The moduli of elasticity (MOE), proportional limit stresses and moduli of rupture (MOR), perpendicular (C⊥type) and parallel (C∥ type) to the grain of face laminae markedly increased or decreased with increasing percentage of core lamina thickness. The percentages of core lamina thickness at which each strength property value of C∥ type became equal to that of C⊥ type ranged from 65% to 80%. At each percentage of core lamina thickness, the MOE and proportional limit stress of C∥ type were higher in C∥(45) specimens having perpendicular-direction lamina of 45° annual ring angle in the core than in C∥(90) specimens having perpendicular-direction lamina of 90° in the core, whereas there was little difference in MOR between C∥(45) specimens and C∥(90) specimens. For 45° specimens having the core lamina thickness from 60% to 70%, MOE as well as MOR parallel and perpendicular to the grain of face laminae exceeded the corresponding requirement values of structural plywood with 21.0-mm thickness specified in Japanese Agricultural Standards.
The measured MOEs of C⊥ type were nearly equal to those calculated from true MOEs of individual laminae, whereas the measured MOEs of C∥ type were smaller than the calculated MOEs, owing to the effect of deflection caused by shear forces. The percentages of deflection caused by shear force versus total deflection (Ys) were much greater in C∥(90) specimens than in C∥(45) specimens. The Ys for the C∥(45) specimen decreased with increasing percentage of core lamina thickness, while Ys for the C∥(90) specimen minimally varied.
References
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