This study aimed to evaluate the physical and mechanical properties of red oak (Quercus spp.), white oak (Quercus spp.), hard maple (Acer saccharum) and yellow-poplar (Liriodendron tulipifera) and compare them to values from past publications. Mechanical testing was conducted on small, clear, defectree specimens from red oak, white oak, hard maple and yellow-poplar following the standard ASTM D143. Percentage of latewood, moisture content, specific gravity, modulus of elasticity (MOE), modulus of rupture (MOR), compression parallel and perpendicular to the grain and Janka hardness were determined. Results indicated that mechanical properties for red oak, white oak, hard maple and yellow poplar have not changed substantially because the average values remain in a range that is very close to the ones published in past studies. Thus, values from the Wood Handbook can still be used for engineering purposes.

I examined the effects of hydrologic gradients and upland timber harvesting with different streamside management zone widths on yellow-poplar (Liriodendron tulipifera) processing and the associated macroinvertebrate community structure in the Cumberland Plateau ecophysic region, U.S.A. Prior to upland timber harvesting, 5.0 ± 0.1 g yellow-poplar leaf packs were constructed, zip-tied to gutter nails, and placed into 7 perennial and 6 temporary stream reaches with similar physiochemical and geomorphic characteristics. From December 2007 to May 2008, 3–5 leaf packs were collected per reach monthly. I found significant differences in the functional feeding group composition. Temporary reaches contained higher shredder, gathering-collector, predator, and total macroinvertebrate abundances. Shredder and total macroinvertebrate biomass was also higher in the temporary stream reaches. Gathering-collector biomass along one measurement was higher in the temporary streams. Perennial and temporary stream reaches contained similar macroinvertebrate diversity. Logging operations occurred from May 2008–December 2008. After logging operations ended, yellow-poplar leaf packs were placed into the perennial and temporary reaches of 3 control and 3 treatment streams (2 with same SMZ width, 1 different). From December 2008–May 2009. Leaf packs were collected monthly. Within the temporary and perennial stream reaches, no significant differences were detected between control and treatment yellow-poplar processing rates. No significant differences were detected between the control and treatment functional feeding group composition in abundance and biomass. Post-harvest, taxon richness increased in both the perennial control and treatment streams, while richness declined in the temporary control and increased in the temporary treatment. My findings indicate that when water is present, organic matter processing will function similarly to downstream reaches that have continual water flow. During seasonal flow patterns, macroinvertebrate communities associated with organic matter are present in temporary streams and may exceed perennial stream reaches in their density and biomass. This indicates that temporary streams are physically suitable habitats for macroinvertebrate fauna and contribute to a stream’s form and function. Overall, no observed distinct response in yellow-poplar processing rates or the associated macroinvertebrate community structure was detected within the perennial or temporary streams. Macroinvertebrate community structure varied spatially and temporally. On the taxonomic level, increases in taxa-specific abundance and biomass remain to be explained. Future research assessing interactions on the taxonomic level might help explain increases or decreases in abundance and biomass in relation to treatment effects. This study documented the response of organic matter breakdown and associated macroinvertebrate community structure during the 1st 5 months after logging. Thus, it is only a snapshot of stream ecosystem response to disturbance. Long-term studies are needed to evaluate full ecosystem response and recovery. Due to uncontrollable factors, I was not able to evaluate the success of different SMZ widths. Results documented should be treated with hesitancy, until full ecosystem response has been documented.

Cross Laminated Timber (CLT) is an engineered wood product consisting of an odd number (three to seven) of lumber layers, which are glued in an orientation of each layer perpendicular to other. After its introduction, CLT has been widely adopted in Europe since 1990s and has quickly become popular in the US in the last decade as a sustainable and cost-effective alternative to traditional building materials such as concrete and steel. The first version of PRG-320 was published in 2012 for the US and Canada to help designers and builders understand the properties of CLT and use it safely. The current version of PRG-320 only allows the use of softwood species for commercial production of cross-laminated timber (CLT) in the US. However, recent studies have investigated the possibility of using hardwood species for CLT and have shown promising results. In parallel to this, the next version of PRG-320 is being revised to include hardwood species. The inclusion of hardwood species is an effort to increase the value of underutilized wood species in the United States. This study presents the results from testing of three-layer and five-layer CLTs manufactured using yellow-poplar (Liriodendron tulipifera) as hardwood and southern pine (Pinus spp.) as softwood in different layers, defined as hybrid CLT. The purpose of this project was to compare the bending and shear properties in the major axis direction of hybrid CLT panels obtained from five-point, four-point, and three-point bending tests with the current ANSI/APA PRG-320 values, and also to evaluate their resistance to shear by compression loading and delamination according to ANSI A190.1 and AITC T110 standards, respectively. The bending strength and bending stiffness, except for some individual groups, as well as the shear strength and shear stiffness values exceeded the Grade V3 from PRG-320. However, the wood failure in resistance to shear by compression loading and face delamination in resistance to delamination were lower than the required values in the standards. The test results demonstrated that CLT groups consisting of yellow-poplar has strength and stiffness properties comparable to those consisting of southern pine. This suggests that yellow-poplar could be a promising alternative species to softwood in the production of CLTs. / Master of Science / Cross Laminated Timber (CLT) is a wood composite material made of lumbers that are oriented perpendicular to each other and glued together. CLT has quickly gained popularity in Europe since its introduction in the early 1990s and has become an attractive material in the United States in the last decade due to its sustainability and cost-effectiveness compared to traditional building materials. As a standardization effort, the first standard for CLT, PRG-320, was published for both the US and Canada as a guide for designers and builders to understand the properties of CLT and has allowed only softwood for the commercial production of CLT in the US since its initial version. The promising results of research on the use of hardwoods in CLT production have enabled efforts to include hardwood species in the next version of the PRG-320. This study presents the results from testing of three-layer and five-layer CLTs manufactured using yellow-poplar as hardwood and southern pine as softwood in different layers, defined as hybrid CLT. The purpose of this project was to compare the bending and shear properties in the major axis direction of hybrid CLT beams obtained from five-point, four-point, and three-point bending tests with current industry guidelines, and also to evaluate their resistance to shear by compression loading and delamination. The test results indicated that yellow-poplar possesses similar strength and stiffness properties to southern pine, indicating that it has potential to be used as an alternative to softwood species in CLT production.

The primary focus of this thesis was to investigate the critical strain energy release rates (G) for mixed-mode (I/II) fracture of wood adhesive joints. The aims of the study were: (1) quantifying the fracture properties of two material systems, (2) analyzing the aspects that influence the fracture properties of bonded wood, (3) refining test procedures that particularly address layered orthotropic systems in which the layers are not parallel to the laminate faces, of which wood is often a particular case, and (4) developing testing methods that enhance the usefulness of performing mixed-mode tests with a dual-actuator load frame. The material systems evaluated experimentally involved yellow-poplar (Liriodendron tulipifera), a hardwood of the Magnoliaceae family, as adherends and two different adhesives: a moisture-cure polyurethane (PU) and a phenol/resorcinol/-formaldehyde (PRF) resin. The geometry tested in the study was the double cantilever beam that, in a dual-actuator load frame, can be used for testing different levels of mode-mixity. The mixed-mode loading condition is obtained by applying different displacement rates with the two independently controlled actuators of the testing machine. Characteristic aspects such as the large variability of the adhesive layer thickness and the intrinsic nature of many wood species, where latewood layers are alternated with earlywood layers, often combine to confound the measures of the critical values of strain energy release rate, Gc. Adhesive layer thickness variations were observed to be substantial also in specimens prepared with power-planed wood boards and affect the value of Gc of the specimens. The grain orientation of latewood and earlywood, materials that often have different densities and elastic moduli, limits the accuracy of traditional standard methods for the evaluation of Gc. The traditional methods, described in the standards ASTM D3433-99 and BS 7991:2001, were originally developed for uniform and isotropic materials but are widely used by researchers also for bonded wood, where they tend to confound stiffness variations with Gc variations. Experimental analysis and analytical computations were developed for quantifying the spread of Gc data that is expected to be caused by variability of the adhesive layer thickness and by the variability of the bending stiffness along wooden beams. / Ph. D.

Thermally modified wood (TMW) contains no toxic components and is recommended for its durability, levels of equilibrium of moisture content, and dimensional stability performance. A limitation of TMW is the lack of market acceptance and products due to insufficient information regarding the performance of commercially available products. The goal of this project was to improve the market penetration and industrial processes of TMW. The first objective was to study the perception of TMW products from architects in North America using a survey instrument. Results revealed that information regarding TMW is not reaching the audience for TMW, and that providing knowledge regarding technical and marketing aspects of TMW is essential to increase the market share. The second objective consisted of the evaluation of the variability of the physical and mechanical properties of three thermally treated species manufactured in North America. Results showed that the performance of the commercially produced material was similar among the three companies, where only in seven out of 24 properties had statistical differences. Properties that were significantly different, did not have large enough differences in means to be realistically noticed by customers and all were highly different from untreated wood. The final objective involved the implementation of Lean thinking to the manufacturing process of TMW with the goal of improving the process with a direct impact on cost and waste reductions. Three companies were used as case studies for the production process. The implementation of Lean thinking in the process proposed a reduction in lead times from 55.47 days to 23.20 days, with an increase in value-added activities from 1% to 6%. Most of these gains were obtained through a reduction in inventory levels. / Master of Science / Thermally modified wood (TMW) contains no toxic components and is recommended for its durability, levels of equilibrium of moisture content, and dimensional stability performance. The current market for TMW encounters a lack market acceptance, due to insufficient information and performance measures. The main goal of this study was to increase market penetration and study the industrial processes for manufacturing TMW, using three specifics objectives. For the first objective, a survey was conducted to study the perception of TMW among architects. The results showed a that there was a lack of information regarding the technical and marketing aspects of TMW products, which needs to be addressed by distributors and producers. The second objective consisted of the evaluation of the variability of mechanical and physical properties of three thermally treated species manufactured in North America. The results showed that the performance from the commercial processes were similar, where only seven out of 24 cases showed statistical differences based on the Analysis of Variance (ANOVA). The final objective consisted of a Lean process strategy to produce TMW, improving the process with a direct impact on cost and waste reduction. To study the production process, three case study companies were used. The proposed Lean process reduced the lead times and value-added activities increased. The primary gain was seen in reducing inventory levels.

The goal of this study was to assess the potential of using hardwood lumber in CLT manufacturing. The goal was achieved by addressing four specific objectives. The first objective was to collect CLT manufacturers' perspectives for using hardwood lumber in the current manufacturing setup. The second objective was to determine hardwood sawmills' current ability to produce structural grade lumber (SGHL) from low value logs as a product mix through a survey of hardwood lumber producers in the US. The third objective was to conduct a log yield study of SGHL production from yellow poplar (YP) logs to produce 6'' and 8'' width SGHL to match the PRG 320 requirements. The fourth objective was to determine CLTs' production cost using SGHL and compared it with the CLTs manufactured from southern yellow pine (SYP). The results suggest that all three CLT industries visited and interviewed had sufficient technology to produce hardwood CLTs. The production of hardwood CLTs was mainly limited by the quality and quantity of lumber available. The hardwood sawmill survey results indicated that, currently, less than 10% of the sawmills had all the resources required to produce SGHL. The current ability of the sawmills was measured based on the resources necessary to begin SGHL production. Forty percent of the sawmills would require an investment in sawing technology to saw SGHL, 70% would require employing a certified lumber grader, and 80% would require a planer to surface lumber. Another significant finding was the sawmills' willingness to collaborate with other sawmills and lumber manufacturers. More than 50% of sawmills were open to potential collaboration with other stakeholders if necessary, which is crucial to commercializing SGHL for a new market. The log yield study of yellow poplar helped demonstrate that the mixed grade lumber production method to convert lumber from lower quality zones as SGHL yields higher lumber volume for sawmills and at the same time reduces lower-grade lumber volume. On average, SGHL production increased lumber volume by more than 6% compared to only NHLA grade lumber production when 65% of the lumber was converted to SGHL. The volume of lower lumber grades from 2 common and below decreased from an average of 85% to less than 30% when producing SGHL as a product mix with NHLA grade lumber. This study observed more than 95% of SGHL as Number 3 and better lumber grades. At estimated lumber value, 2x6 and 2x8 SGHL and NHLA grade lumber production as product mix from a log generate higher revenue for all log groups except for the diameter 13" logs. A lower percentage of higher-grade lumber was observed for diameter 13’’ logs than other log groups from this experiment, which resulted in lower revenue. Production cost of CLTs was determined based on the lumber value to manufacture 40' x 10' plain panels with different combinations by lumber grade of yellow poplar and southern yellow pine lumber alone. Production cost was determined by assuming that lumber value contributes 40% of CLTs' total production cost. The 3- ply CLT panels were manufactured using S. Selects lumber in a major direction, and No 1-grade lumber in the minor direction from YP had a production cost of $662.56 per cubic meter, which cost only $643.10 when SYP lumber was used at referenced lumber value. This study concludes that CLT panels from YP cost 3-7 % more than SYP-CLTs at the referenced lumber values. / Ph.D. / This research aims to expand the hardwood lumber consumption in the US by evaluating the opportunity to manufacture cross-laminated timber (CLTs). First, CLT manufacturing industries were visited to know their current capacity to process hardwood lumber. The results suggest that all three CLT industries had sufficient technology to produce hardwood CLTs, and the production was mainly limited by the quality and quantity of lumber available. Commercially hardwood can be used in CLT manufacturing if it can be used for structural application. Hardwood lumber must meet the structural application's minimum requirements to manufacture the structural grade CLTs, so we surveyed the hardwood sawmills to know if they have the required resources to manufacture the structural grade hardwood lumber (SGHL). Only ten percent of the sawmills had required technology to produce SGHL without additional investments. Production of the SGHL also required to generate more revenue for the hardwood sawmills, so we conducted the log yield study to know how the revenue structure of sawmill operation will change from the mixed grade lumber production. At estimated lumber value, 2x6 and 2x8 SGHL and 1-inch National Hardwood Lumber Association (NHLA) grade lumber production as product mix from logs generate higher revenue for all log groups except for the diameter 13" logs. Finally, the production cost of SGHL from the log yield study was evaluated and used to produce CLTs at 40% production cost from lumber at 15% profit margins for sawmills and compare with southern yellow pines CLTs. The results indicate that yellow poplar CLTs cost 3-7 % more than southern yellow pines CLTs at the referenced lumber values. This study concludes that hardwood lumber can be used in CLT manufacturing, so there is an opportunity for hardwood sawmills to expand the market. The first step for commercial production of hardwood CLTs is to produce SGHL on a commercial scale, given that sawmills can benefit from these new products in the current lumber market and meet the minimum requirements of the CLT raw materials.

Literature shows that production of cottonseed adhesives is feasible to develop an environmentally friendly and competitive bio-based wood adhesive. Defatted cottonseed and water-washed cottonseed meals were prepared from glandless cottonseed and were used in adhesive formulations to produce three-ply yellow poplar (Liriodendron tulipifera) plywood panels as the first objective. These two cottonseed meals were compared with the properties of plywood panels made with an adhesive formulated from a commercial soybean meal, as a control. Adhesive resins were prepared from each protein meal with sodium metabisulfite (Na2S2O5) and one of two polyamido-amine-epichlorohydrin (PAE) wet strength agents, and the plywood panels were produced by hot pressing for 7, 8.5 and 10 minutes at 135°C with a constant pressure of 1.241 MPa. Panels prepared from three protein meals had comparable shear strengths. The combinations of the two cottonseed preparations and the two wet strength agents produced panels with acceptable wet resistant properties, whereas the soybean meal only produced acceptable panels with one of the wet strength agents. Because the panels prepared from the two cottonseed meals had comparable properties, there appears to be no benefit to including a water-washing step to increase the meal’s protein level. The second objective of this research was to reduce the hot press time and develop cottonseed meals into adhesives to become comparable to commercial soybean-based adhesives. New cottonseed, water-washed cottonseed, and commercial in-house soybean meals were separately prepared with deionized water, sodium metabisulfite, and PAE to produce three-ply yellow poplar plywood panels. The panels were hot pressed for 4, 5, and 6 minutes at 135°C with a constant pressure of 1.241 MPa. Panels prepared from the three meals and commercial soybean plywood panels had comparable mechanical shear strengths and water resistance properties. Results indicated that press time, meal types, and interactions were statistically significant. Shear strength results indicate that cottonseed could be used alternatively to soybean. The new cottonseed panels were more resistant to delamination than soybean. The cottonseed meals showed great promise for applicability as a formaldehyde-free, bio-based, and environmentally friendly hardwood plywood wood-based adhesives product for use in interior type applications.

Several researchers have concluded that there is little or no relationship between specific gravity and ring width or growth rate in yellow-poplar (Liriodendron tulipifera L.). Because most mechanical properties of wood are also closely related to specific gravity, it would thus be of interest to learn how minimum suppression and maximum release years' evidence that can be extracted from radial growth patterns based on a modified radial growth averaging (RGA) technique's influence the compression parallel to grain strength and specific gravity of wood. This study is designed to evaluate the effects of growth suppression and release on ultimate crushing stress and specific gravity for small-sized yellow-poplar specimens. Additionally, the relationship between specific gravity and ultimate crushing stress is investigated. Twenty-three yellow-poplar cores were examined for their growth ring widths. Minimum suppression and maximum release years were identified based on the modified RGA criteria method. From each increment core, three 1 Ã 1 Ã 4 mm specimens from both minimum suppression and maximum release years were tested for their ultimate crushing stresses using a micro-mechanical test system. The specific gravity of each specimen was also recorded. These data were analyzed using a paired samples t test and a simple linear regression. The results indicate that the mean ultimate crushing stress and specific gravity of maximum release years were significantly higher than that of minimum suppression years. Furthermore, the ultimate crushing stress was linearly related to the specific gravity of the specimens. / Master of Science