Survey of selected adhesive bonding properties of nine European softwood and hardwood species

Johannes Konnerth,Milica Miljković,Wolfgang Gindl-Altmutter,Marcel Kluge,Georg Schweizer

doi:10.1007/s00107-016-1087-1

Johannes Konnerth, Milica Miljković + Show 3 more

Open Access

https://doi.org/10.1007/s00107-016-1087-1

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Abstract

Due to the increasing interest in applying a wider range of wood species for structural purposes, nine European softwood and hardwood species (ash, beech, birch, hornbeam, larch, oak, poplar, black locust and spruce) were assessed for their ability to be bonded with three different commercial adhesive systems (melamine–urea–formaldehyde, one-component polyurethane and phenol–resorcinol–formaldehyde). Tensile shear strength and delamination tests were conducted according to European standards, for all tests including the corresponding wood species as adhesive joints and as a solid wood reference. When tested in dry condition, the threshold of solid wood tensile shear strength was reached by all species–adhesive combinations. By contrast, testing in wet condition revealed distinct performance reductions for certain combinations. This trend was confirmed by delamination testing. Overall, the results indicate that extrapolation of test results achieved with a specific wood species (as recommended in the current standard for lap-joint tests) towards other species is highly problematic and has to be done with caution.

Highlights

Wood from deciduous trees is of growing interest for structural purposes due to a couple of notable features
Due to the increasing interest in applying a wider range of wood species for structural purposes, nine European softwood and hardwood species were assessed for their ability to be bonded with three different commercial adhesive systems
The aim of the present study is to provide an overview of the bond performance of a wider range of European deciduous and coniferous wood species bonded with three currently available standard adhesives systems of different chemistry and mechanical properties (Stoeckel et al 2013), with indicated suitability for bonding at least one deciduous wood species for an indicated service class

Summary

Introduction

Wood from deciduous trees is of growing interest for structural purposes due to a couple of notable features. A couple of hardwood species such as ash, beech, birch, oak and others possess higher mean density values ranging up to 670–770 kg/m3 (Wagenfuhr 2007). For this reason they typically exceed the mechanical properties of the main softwood species Norway spruce having an average density of 470 kg/m3 (Wagenfuhr 2007). Several types of hardwood such as oak or Robinia possess excellent natural durability (Pitzner et al 2001), others are treatable, for example by impregnation with preservatives to increase their durability. The variety of species with regard to their optical appearance gives the potential to increase the attractiveness for their esthetic design diversity

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