Sustainable Timber Materials

Researchers Lead Key Studies on Sustainable Timber Materials

Emily Smudde, reprinted from WSU News

Even as he dug his hands deeper in the pockets of his zipped-up coat to protect against the cold wind, Todd Beyreuther smiled.

“There is a great amount of wind exposure at this site; it will work really well for testing,” said Beyreuther, an assistant research professor at Washington State University’s Composite Materials and Engineering Center and Institute for Sustainable Design.

The muddy ground where he stood on the new Eggert Family Organic Farm is the future location of the farm’s pavilion; a small structure that will be built with prefabricated, customizable walls meant to withstand high winds, extreme temperatures, and whatever else nature may throw at them.

“The research brings together materials science, structural engineering, and design.”

The walls will be the first prototypes of the hybrid cross-laminated timber panels with customizable wood composite cores that Beyreuther and his team are developing at WSU.

In addition to coordinating the integrated design of the farm with students, faculty, and professional partners, Beyreuther is leading a grant from the USDA to develop advanced modeling and digital fabrication methods to make high- performance cross-laminated timber (CLT) panels.

“CLT is like plywood on steroids,” said Don Bender, director of the Composite Materials Engineering Center. “It involves alternating layers of stress-rated lumber to form thick plates that have advantages such as carbon sequestration, reduced construction times, and superior fire resistance.”

Developed and used all over Europe, CLT panels are gaining popularity in North America because of their varying sustainability and time-saving characteristics. In addition, CLT can use lower quality timber including pine beetle kill wood, which is a large problem in the forests of the inland Northwest. The wood comes from lodgepole and ponderosa pines that are weak, dying, and stained blue because of infestations of mountain pine beetles. Harvesting the infected wood protects forests from fires and tree rot that leads to increased carbon emissions.

On its own, CLT is emerging as a favorite in the architecture, engineering, and construction industry due to its mass- customization characteristics at a building scale, and now Beyreuther and his team are developing the ability to further mass- customize the panels. Their work will enhance structural, hydrothermal, and acoustic performance of the panels.

“How we manufacture wood can now be in sync with what architects and others in professional practice do,” said Beyreuther. “The research brings together materials science, structural engineering, and design.”

The modeling scripts Beyreuther is developing will plug into modeling and analysis programs common in professional practice, allowing architects and engineers to input different environmental and design factors that will impact the building. A company that manufactures CLT panels can then tune the cores accordingly, reinforcing the walls that need to hold extra weight or withstand earthquakes, making others more heat absorbent, and so on.

The project also includes existing subtractive manufacturing methods of cutting and milling, and proposes advanced additive methods to essentially 3D print with wood.

“It’s the next generation of CLT technology,” Beyreuther said.

In addition to providing a sheltered location where students will process harvested food and farm visitors can enjoy a view of fruit trees and Palouse hills, the pavilion will be one of the first test beds of this technology. The CLT cores will be embedded with technology that tests state-of-the-art seismic and wind energy dissipation mechanisms important to build tall wood buildings up to 20 or 30 stories.

Sensors embedded in the wall will monitor the amount of stress the building undergoes, both horizontal stress from wind and vertical stress from gravity loads such as snow. The panels will also enclose three spaces at different temperatures to measure how heat and moisture move in and out of the walls. A similar experiment will be conducted concurrently in Puyallup to compare different climates, including the wet marine climates of the large urban centers in the Pacific Northwest.

Beyreuther and his team will model and prototype the hybrid CLT panels at the Composite Materials and Engineering Center.

Students will also get hands-on experience with this new technology, helping in the modeling, fabrication, and construction. The farm pavilion, complete with its hybrid CLT panels, will provide opportunities for interdisciplinary research and education in design and engineering.

“This is a small farm operations structure, but it will have novel, performance-based wood building technologies that will be relevant to the architecture, engineering, and construction community as they look toward carbon neutral solutions for tall, urban buildings,” Beyreuther said.