Flexural and Shear Performance of Wood Composite Panel with Embedded Cross-Laminations

The structural behavior of an innovative wood-based composite system, manufactured out of $2\times 6$ southern yellow pine lumber, was studied through destructive experiments. The composite panel system consisted of profiled 34.9-mm-thick surface laminations with precut rectangular grooves and 25.4-mm-thick cross-laminations fitted (embedded/dadoed) into the grooves. The cross-laminations were oriented across the surface layers at a specified repetitive spacing. Given that the 34.9-mm-thick surface laminations were in direct contact with each other in those places where the cross-laminations were absent, the total depth of the panels was 69.9 mm. The flexural and shear performance of this composite system, which is called embedded cross-laminated timber (ECLT), were compared against that of the conventional three-ply cross-laminated timber (CLT) panel with the same thickness. The ECLT panel specimens were expected to perform better than the CLT panel specimens in bending because they have more wood fibers aligned parallel to their neutral axes. The effective bending stiffness ($E{I}_{\mathrm{eff}}$) and moment carrying capacity of the two composite systems were obtained by conducting four-point bending tests at a span-to-depth ratio of $26.4:1$. The ECLT specimens exhibited an average moment carrying capacity of $10.9\times {10}^6\mathrm{N}·\mathrm{mm}$ and $E{I}_{eff}$ of $89.4\times {10}^9\mathrm{N}·{\mathrm{mm}}^2$, while the conventional CLT specimens achieved corresponding properties of ${10.2\times 10}^6\mathrm{N}·\mathrm{mm}$ and $84.2\times {10}^9\mathrm{N}·{\mathrm{mm}}^2$, respectively. Also, the effective shear stiffness ($G{A}_{eff}$) and shear force capacity of the composite systems were estimated and measured, respectively, by conducting four-point bending tests at a span-to-depth ratio of $11.6:1$. On average, the ECLT specimens resisted the shear force of $38.2\times {10}^3\mathrm{N}$, while the conventional CLT specimens resisted $36.7\times {10}^3\mathrm{N}$. The average estimated $G{A}_{eff}$ values of ECLT and CLT were $2.57\times {10}^6\mathrm{N}$ and $1.93\times {10}^6\mathrm{N}$, respectively. Thus, these study results indicate that the proposed cross-laminated wood composite product might outperform conventional CLT in the major direction under bending.