Banner for LabNotes
From Lab Notes
Contact Information
Forest Products Laboratory
One Gifford Pinchot Drive
Madison, WI 53726-2398
Phone: (608) 231-9200
Fax: (608) 231-9592


You are here: FPL Home  / Information Products & Services  / Publications

Requested Product

Title: Small scale test to measure the strength of adhesives at elevated temperatures for use in evaluating adhesives for cross-laminated timber (CLT)

Source: Wood & Fire Safety, 2020. 3-8.

Author(s)Zelinka, Samuel L.; Miyamoto, Byrne ; Bechle, Nathan J.; Rammer, Douglas

Publication Year: 2020  View PDF »

Category: Journal Articles
Associated Research Project(s):   FPL-4714-2B   FPL-4716-2A

Abstract: Cross laminated timber (CLT) is becoming widely available in North America. The product standard for North American CLT, PRG-320, has strict requirements on adhesive performance under fire scenarios. To become an adhesive certified under PRG-320, a full sized CLT compartment must be built and tested without a second flashover occurring caused by delamination. Currently, only three adhesive formulations are PRG-320 certified. This large scale test is expensive to run and only yields “pass-fail” results. In this paper we present small-scale adhesive tests performed at the Forest Products Laboratory. The tests examine a single lap shear joint. The samples are tested at elevated temperatures in a universal testing machine with an environmental chamber built around the grips. The strains are measured using digital image correlation. Tests were conducted in two different manners. In the first test, thermal equilibrium was achieved and the sample was loaded to failure. In the second test, a constant load was applied and a thermal ramp was applied until failure occurs and the temperature at failure was recorded. Importantly, the tests were compared against control samples of solid wood (no adhesive) so that adhesive strength could be normalized to that of solid wood. It is hoped that this small-scale test can aid in the understanding of CLT adhesive performance and be used to screen adhesives prior to investment in large scale adhesive qualification tests.

Keywords: Mass timber; adhesives; elevated temperatures; strength; polyurethane; creep

Publication Review Process: Formally Refereed

File size: 664 kb(s)

Date posted: 09/23/2020

This publication is also viewable on Treesearch:  view
RITS Product ID: 99401
Current FPL Scientists associated with this product (listed alphabetically)
Rammer, Douglas R.
Research General Engineer
Zelinka, Samuel L.
Materials Research Engineer

Additional items that might interest you
View the video celebrating FPL's 100 years of public service in 2010, from the producers of the Greatest Good....view

Research Highlights from FPL....view

Termite Eradication: A search for the Holy Grail.... view

Moisture Management in Residential Construction Series videos...view

Wood Floor Systems in Residential Construction Series videos....view
- FPL's Mission and Strategic Plan -

FPL's mission is to identify and conduct innovative wood and fiber utilization research that contributes to conservation and productivity of the forest resource, thereby sustaining forests, the economy, and quality of life. ... ..more »

- FPL Research Emphasis Areas -
Advanced Composites

As an integral part of the FPL mission, we improve the long-term sustainability of our Nation's forests by creating valuable composite products from biobased materials ... ..more »

Advanced Structures

The FPL has been in the forefront of wood-frame housing research since 1910 and has long been recognized as a world leader in such housing-related areas as engineered wood ... ..more »

Forest Biorefinery

We all know the compelling reasons that the United States needs to reduce its dependence on fossil fuels. Historically, the greatest increases in energy demand have been for transportation fuels ... ..more »


A leader in wood products research for over a century, the FPL is positioning itself to become the lead Federal research facility for the application of nanotechnology in forest products ... more »

Woody Biomass Utilization

Forests in the United States contain a substantial amount of small-diameter, overstocked, and underutilized material.FPL research projects are exploring the potential of the small-diameter ... ..more »