The performance of adhesive systems for structural timbers

Abstract

Structural adhesives can be used to bond two or more timber components together and to bond-in other materials in such a way that they transfer load between the elements. In addition to this, owing to the nature of timber, the adhesive will often have to possess some gap-filling properties. Traditionally, formaldehyde-based adhesives have been used, but these have limited gap-filling qualities and often require the application of pressure to the joint to achieve the required strength. Alternative structural timber adhesives, such as epoxy resins and polyurethanes, have been used in certain fields of timber engineering. One of these areas is in the repair of timber structures, where better gap-filling qualities are required and the application of pressure is not practical. TRADA Technology Ltd (TTL) has been investigating the application of epoxy resins in the repair of structural timbers. Initial research has examined the methods in which epoxy resin is used in such situations. Aspects such as the effect of timber moisture content on joint strength have been investigated. Forthcoming tests will examine the effect of surface preparation and the long-term performance of specimens under load in exposed conditions. Timber has a long history of use as a structural building material and finds its way into many varied applications, from shipbuilding and marine architecture to civil and structural engineering.