InTrans / Aug 14, 2018

Improved Understanding of Moisture Effects on Outdoor Wood-Adhesive Bondlines

Repairing historic covered bridges often requires using wood construction materials, such as plywood or laminated veneer lumber, that rely on adhesives for their structural integrity. Although the roof structure keeps the heavy timber trusses well sheltered and dry enough that they have survived 100 to 200 years, humidity changes caused by weather still affect the bridge materials. Of particular concern is how the swelling and shrinking of wood with changing humidity contributes to wood-adhesive bondline failures. When bondlines fail, costly repairs are needed to maintain historic covered bridges. In this study, we use new sophisticated techniques to probe interactions between moisture, adhesives, and wood to better understand what causes moisture-related failures in wood-adhesive bondlines.