Project contact is Vikram Yadama at Washington State University
The broader impact/commercial potential of this PFI project is in development of a commercially-viable process for manufacturing high-performing, durable mass strand timber panels for building construction from low-value and underutilized small-diameter softwood trees, such as from hazardous fuel thinning operations for improved forest health. The broader impacts are: (1) advancement of discovery and understanding while promoting teaching, training, and learning by including students and faculty in the research; (2) enhancement of infrastructure for research and education by establishing collaborations between interdisciplinary, yet complementary academic and industry stakeholders; (3) broadening of research dissemination to enhance understanding by involving industry and academia in the research, publishing project results in diverse media sources, and presenting research results in several formats that will benefit a wide range of forest products industry stakeholders; and (4) improved economic competitiveness of the U.S. forest products industry. In addition, if this proof-of-concept research leads to commercial applications, the benefits to society are: (1) new products with reduced environmental impacts, improved durability, and longer service-life; (2) technology that increases the U.S. forest products industry's competitiveness through creation of new jobs and increased opportunities for potential exports; and (3) increased use of wood, an environmentally-friendly, renewable, sustainable, and carbon-sequestering material.
The proposed project addresses challenges facing cross-laminated timber (CLT) panels in mass timber construction. Construction currently requires extreme care to protect CLT panels from moisture while ensuring long-term durability. Although builders take measures to reduce moisture exposure, it is inevitable that the CLT panels will take on water during their service-life. This project addresses these problems by utilizing thermal modification to produce chemical-free, mass timber panels with increased resistance to moisture and decay and improved dimensional stability. The goals are to: (1) evaluate process-performance relationships for thermal modification of small-diameter wood strands, and (2) demonstrate the feasibility of manufacturing high-performance cross-laminated strand-veneer lumber (CLSVL) mass timber panels. The objectives are to: (1) demonstrate the feasibility of utilizing thermally modified laminated strand veneer lumber for production of high-performance CLSVL panels, and (2) determine the potential environmental impacts of the new CLSVL panels. The technical results include validation of a repeatable process for thermally modifying small-diameter pine strands, validation of a method for manufacturing CLSVL panels, verification of physical and mechanical performance of the CLSVL panels, and establishment of commercially-viable process-performance relationships to enable commercial production of the CLSVL mass timber panels.
Project contact is Karl Englund at Washington State University
Cross laminated timber (CLT) has energized the wood industry, not only throughout the US but also across the globe. Potential for lower construction costs and a sustainable building material has provided proponents of CLTs the fuel for their growth. However, to obtain lower feedstock costs and provide a truly sustainable building product the use of small diameter timber (SDT) and other lower quality woods is imperative, but not yet realized. The out-of-plane (OOP) defects such as twist, cup and bow commonly found in SDTs, make processing CLTs prohibitive due to the press load requirements that are needed to “flatten” these defects out and create intimate contact at the glue line. Due to this issue, many CLT manufacturers utilize high grade lumber, while SDT and other low value woods are culled out and not used. Our proposal will characterize the OOP defects commonly found in SDT Douglas-fir (DF) and ponderosa pine (PP) from the Inland Northwest, will develop a tool to calculate anticipated forces to compress out the OOP defects and evaluate the durability performance of a full-scale CLT panel that includes commonly rejected lumber from SDT due to presence of OOP defects. The tool developed in this project will provide the CLT industry with the know-how to determine the press loads required to make a panel from SDT feedstocks and how to lower these accumulated loads through reducing or changing the laminate cross-sectional dimensions. Results of this study will promote increased utilization of SDT lumber, currently rejected, for CLT production and will contribute to healthy forests and rural economic development.
This thesis is part of a larger project where lumber from small logs harvested in restoration programs was examined for use in CLT; panels were manufactured utilizing lumber from small logs and the mechanical properties were assessed. While another team focused on mechanical testing to examine the technical viability of this concept according to current manufacturing standards, the objective of this thesis was to assess the practical feasibility of this conception within the supply chain (C. Lawrence, 2017). This research focuses on the Blue Mountains–a region in eastern Oregon.
The approach was based on analysis of previous literature, Forest Service Cut & Sold reports, and semi-structured in-person and telephone interviews of federal timberland foresters, sawmill personnel, and management of current and potential cross-laminated timber manufacturers.
This research suggests that if the regional supply chain in the Blue Mountains were to process more small diameter logs into lumber, this will increase the available supply of 2x4 and 2x6 dimensions of lumber for use in a variety of different markets rather than for exclusive use in the center layers of cross-laminated timber panels.
Creating a value-added product using low-grade lumber produced from small-diameter timber would improve the economic balance for forest restoration operation. The general aim of this research was to increase or stimulate markets for wood products utilizing low-value small-diameter material generated in National Forest System restoration programs. Our hypothesis is that low-value lumber cut from small-diameter logs (4”-6” at the small end) could be successfully utilized in core layers of structural cross laminated timber (CLT) panels.
However, to be qualified for structural uses, CLT must meet standard minimum bond integrity criteria specified by the North American product standard (ANSI/APA PRG 320-2012), determined through laboratory testing for delamination (=5%) and shear resistance (=80% wood failure). The objective of this project was to determine the feasibility of small-diameter logs harvested from National Forest System restoration programs in 3- and 5ply CLT panels. Adding value to low-value timber harvested from USFS lands by using it within CLT applications is expected to increase profitability of the harvested timber, offsetting costs for the restoration programs. The specific objectives were to: (1) build and test CLT panels utilizing lumber from forest restoration operations in core layers of panels against the certification criteria per PRG 320-2012 to allow low-grade lumber in cores of structural CLT; (2) based on findings, propose respective changes to the current North American standard PRG 320-2012; and (3) investigate the efficiency of the primary processing of small-logs from the thinnings and lamination options with lumber produced from these small logs.