7. Effect of Wood Characteristics on Adhesive Bond Quality of Yellow-Poplar for Use in Cross- Laminated Timbers

摘要

Cross-laminated timber (CLT) panels are gaining more and more interest in North America, though CLTs are currently only approved for manufacture under ANSI/APA PRG-320 using select softwood species. Much of the low-grade Appalachian hardwood lumber produced has potential for being used to produce CLT panels given that the necessary research data is developed to show that hardwood CLTs meet the requirements of the standard. One particular issue with using hardwood lumber in CLT panels is that it is often more difficult to achieve a strong, durable adhesive bond. Among the Appalachian hardwood species, yellow-poplar (Liriodendron tulipifera) is particularly abundant in West Virginia. The objective of this research was to identify which characteristics of yellow-poplar lumber have an effect on adhesive bond quality. Twelve treatments were applied to yellow-poplar lumber to examine the interactions and main effects of adherend thickness, lamination orientation, and orthotropic orientation (saw pattern). Bond strength and durability was determined using shear-block and cyclic delamination tests. Fluorescence microscopy was used to determine the level of adhesive penetration achieved on select samples that performed notably well or poorly. Results related to the effect of yellow-poplar lumber characteristics that result in the most desirable adhesion properties will be presented and compared to a softwood control species that is currently accepted for manufacturing.