2. Forum Wood Building Baltic 2021 EN17334 – a first-time user experience | Karlis Pugovics
EN 17334 – a first-time user experience Karlis Pugovics, researcher1, guest lecturer2; Uldis Spulle, senior researcher2; Kristians Klancbergs, student2 1 2
Forest and Wood Products Research and Development Institute, Latvia Latvia University of Life Sciences and Technologies, Latvia
Summary If one has to sum up modern motto for timber construction, citius – altius – fortius seems to be an appropriate phrase. Advents in materials and, perhaps more importantly – fastening systems have made large scale timber construction the modern reality. Gluedin rods have been a hot topic in timber engineering research field for many years now. A great deal of problems regarding consistent results can be attributed to lack of unified testing standards. Advent of EN 17334 provided research community with a unified method for testing. This paper reflects the first-time user’s experience working with this standard; problems experienced and potential solutions. Key words: glued-in rods, EN 17335, adhesive testing, dense epoxy adhesive.
1. Introduction EN 17334 specifies performance requirements and methods for determining characteristic bond strength values for two-component epoxy (EPX) and polyurethane (PUR) adhesives. Performance requirements are tested by the following testing methods: • Tensile shear test (modified EN 302-1 method). • Delamination test (modified EN 302-2 method). • Shrinkage stress test (modified EN 302-4 method). • Multiple compression shear test (modified EN 302-8 method). As stated before, this paper reflects experience and lessons gained during tensile shear testing processes, which were done before more thorough tests regarding performance of glued-in rods.
2. Methods For tensile shear tests a dense (density around 2.00 in with ASTM D792, viscosity 300 000 mPa∙s) two component EPX based adhesive was used. Dense adhesive was chosen with regards to ease future industrial application in factory setting. Three types of samples were made from European Beech (Fagus Sylvatica) in accordance with modified EN 302-1 requirements, using different adhesive line thicknesses: close contact glue line (<0.3 mm) and thick glue lines (1 mm and 2 mm) as seen in Fig. 1. Five different treatment programs were used in testing, named A1 to A5 as per standard requirements. 12 specimens for each sample population were fabricated in order to produce 10 valid test results. Beech elements were conditioned in standard climate of 20 ⁰C ± 2 ⁰C and 65 RH ± 5 RH for 30 days before bonding resulting in average MC of around 12 %, average density of beech elements was calculated to be 745 kg∙m‒3. Beech elements were made from untreated, straight grained material in order to ensure reliable test results.
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