North American cross laminated timber is currently made of softwood lumber following the guidelines of the ANSI/APA PRG-320 manufacturing standard. In this study, the potential of manufacturing CLT panels using various hardwood species and engineered wood products (EWP) was investigated for their compatibility and the impact on the dimensional stability and aesthetics of the end products. Yellow birch, trembling aspen, sugar maple, laminated strand lumber (LSL) and laminated veneer lumber (LVL) were compared to 100% spruce-pine-fir group species (SPF) lumber made CLT panel. The bond line performance of the assemblies was tested as well as the dimensional stability and appearance of the panels when subjected to conditions with equilibrium moisture contents (EMC) of 4.5%, 12% and 16%. Results showed that higher density hardwood species were prone to delamination. LSL, LVL and trembling aspen yielded promising delamination results. Best overall dimensional stability results were achieved with EWP inclusive configurations. Aesthetic integrity assessment showed that the use of hardwood for the core layer and edge gluing of softwood outer layers had a negative impact. Overall, the study showed a great potential for manufacturing future composite CLT (CCLT) products using EWP and low density hardwood species. The cost premium of using these alternative materials would need to be offset by valuable sets of properties or by a reduction of the manufacturing cost.
The purpose of this study is to examine the mechanical properties of ACQ-treated glulam made from three hardwood lumbers. Two nondestructive methods, ultrasonic wave and tap tone method, were also used in this study. The results showed that the dynamic MOE and static MOE of lumbers decreased with increased ACQ preservative retention. ANOVA showed no significant difference in the MOE values of glulam between untreated and ACQ-treated group. However, it was also found that glulam made from red oak lumbers had the highest bending strength retention ratio. The shear strength of the glulam also showed similar results. Finally, no delaminating was found in all glulams after the specimens under soaked and boiled delamination tests.
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