Contents lists available at ScienceDirect International Journal of Adhesion and Adhesives journal homepage: www.elsevier.com/locate/ijadhadh Evaluationofastructuralepoxyadhesivefortimber-glassbondsundershear loading and diferent environmental conditions Žiga Unuk, Andrej Ivanič, Vesna Žegarac Leskovar, Miroslav Premrov, Samo Lubej ∗ University of Maribor, Faculty of Civil Engineering, Transportation Engineering and Architecture, Smetanova Ulica 17, 2000 Maribor, Slovenia ARTICLEINFO Keywords: Epoxides A Glass B Wood and wood composites B Finite element stress analysis C Shear test Varying environmental conditions ABSTRACT This article presents a study of timber-glass adhesive joints. It examines the shear specimen and shear tools preparationprocessandtheevaluationoftheresultsbackedupwithanoverviewofexistingsimilarstudies.The chosen adhesive was a cold-curing two-component structural bonding epoxy resin (Mapei Adesilex PG1). The sheartestswereperformedunderdiferenttemperaturesandthetimbersampleshaddiferentmoisturecontents. A simple shear test tool was designed and was clamped into a universal testing machine for the shear test. The forceandcrossheaddisplacementvaluesfromtheuniversaltestingmachinewereusedforevaluatingtheresults. The environmental conditions of 20°C and 5% timber moisture content resulted in the highest average shear strength obtained from the shear tests of the analysed joints (9.89MPa), whereas the environmental conditions of50°Cand20%timbermoisturecontentresultedinthelowestaverageshearstrength(3.42MPa).Itwasfound that the joint strength is dependent on the environmental temperature and timber moisture content. Moreover, the shear specimen load-displacement behaviour at the environmental temperature of 50°C was linear and nonlinear – depending on the timber moisture content. The most frequent failure type was timber failure. Additionally, a nonlinear contact fnite element analysis was performed to demonstrate the additional shear specimen rotation due to the clearance between the shear specimen and shear tools. This impact was evaluated regarding the stress distribution in the bond line. The evaluated epoxy resin adhesive was proved to be suitable for timber-glass bonds. 1. Introduction Composite timber-glass structures or structural components have become an important and acknowledged segment of modern building construction. For a presentation of the timber-glass structures feld progress in the last years see for example Žegarac Leskovar and Premrov's work [1] or Blyberg's et al. study [2]. Although glass is a transparent material with relatively high strength (compared to timber), it has a negative feature of brittle behaviour. However, when glass is combined with timber, the resulting structure can have some ductility and is, therefore, safer than a similar structure consisting so- lelyofglass.Anexampleofaductiletimber-glassstructuralelementare timber-glass composite beams (see for example Rodacki's et al. study [3] where all investigated timber-glass beams failed in a ductile manner). There are several examples of timber-glass composites, which can be roughly arranged into three groups: besides the aforementioned timber-glass beams (see for example Premrov et al. [4]) there are also timber-glass wall panels (see Fig. 1 andBeretal.[5]) and timber-glass foor/roof panels (see for example Cruz and Pequeno [6]). Asglassisabrittlematerial,oneofthemostimportantpropertiesof the adhesives is their stifness. A lower adhesive stifness ensures more evenlydistributedstressesatthebondedinterfacebutisusuallyalsoan indicator of lower adhesive strength. Diferent adhesive types have been tested in various studies: from fexible silicone adhesives to semi- rigid adhesives like polyurethane and to rigid adhesives like acrylate and epoxy. Regarding the rigidity/fexibility limit values, the standard BSENISO527-1:2012canbeconsidered,asitisfrequentlyusedforthe determination of mechanical properties of adhesives. Adhesives with elastic moduli greater than 700MPa can be considered rigid, with elastic moduli greater than 70MPa and less than 700MPa semi-rigid and with elastic moduli less than 70MPa fexible. According to Banea et al. [8], thinner adhesive layers are preferred over thicker adhesive layers, due to lesser stress concentrations, however, ductile adhesives mightperformbetterwithslightlythickeradhesivelayersastheenergy can be dissipated more in a greater volume. As ductile adhesives are usuallyalsofexibleandviceversa(accordingtoCampilhoanddaSilva https://doi.org/10.1016/j.ijadhadh.2019.102425 Received 6 July 2019; Accepted 30 July 2019 ∗ Corresponding author. E-mail addresses: ziga.unuk@um.si (Ž. Unuk), andrej.ivanic@um.si (A. Ivanič), vesna.zegarac@um.si (V. Žegarac Leskovar), miroslav.premrov@um.si (M. Premrov), samo.lubej@um.si (S. Lubej). International Journal of Adhesion and Adhesives 95 (2019) 102425 Available online 19 August 2019 0143-7496/ © 2019 Elsevier Ltd. All rights reserved. T