Date of Graduation

2015

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Wood Science and Technology

Committee Chair

David DeVallance

Committee Co-Chair

Benjamin Dawson-Andoh

Committee Member

Shawn Grushecky

Abstract

Cross-laminated timber (CLT) panels are gaining 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 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 (bonding surface plane). Bond strength and durability were 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.;The results of the research found that lamination orientation significantly affected bond strength in yellow-poplar, with parallel laminated samples yielding higher average shear strength and wood failure than perpendicular laminated samples. Furthermore, adherend thickness also appears to influence bond strength, as the samples with thinner adherends had significantly higher levels of wood failure in shear block specimens. None of the tested effects had a clear impact on bond durability. Lastly, in comparing the results of the yellow-poplar samples to a reference species (hard pine) that is accepted for CLT manufacture, no differences were noticed in percentage of wood failure or delamination (bond durability). Yellow-poplar had a significantly higher mean shear strength than the reference samples, but this may tell more about the wood itself than the adhesive bond strength. Based on the findings of this research, yellow-poplar could facilitate adhesive bonds of the necessary strength and durability to be used in CLT manufacture.

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