20.500.12556/RUL-185153 Effect of moisture content, surface preparation and lamellae orientation on Mode II strain energy release rate of polyurethane-bonded beech wood Understanding the Mode II fracture behavior of adhesive joints in hardwood species is essential for reliable structural design in timber engineering. This study investigates the shear fracture energy (GII) of polyurethane (PUR)-bonded European beech wood (Fagus sylvatica L.) under two different moisture contents. Three-point bending end-notched flexure (3ENF) tests were conducted on bonded specimens conditioned at 12% and 18% moisture content (MC), with three types of bonding surface preparation: planed, planed + sanded, planed + primer prior to bonding. Crack initiation and propagation were monitored using 3D digital image correlation (DIC) and fracture energy was calculated using the compliance-based beam method (CBBM). The results reveal a clear influence of both moisture content and surface treatment on Mode II fracture behavior. Higher moisture content consistently reduced Gc and stress values, while specimens with different lamellae orientations achieved the highest stresses before adhesive joint failure occurred. Different bond failures and their influence on fracture behavior are also discussed. The critical Mode II strain energy release rate, GIIc, was defined at the maximum applied load corresponding to the onset of unstable crack propagation, as confirmed by synchronized DIC measurements. The findings contribute to an improved understanding of shear behavior in PUR-bonded hardwood joints and offer valuable input for cohesive zone modelling and structural performance prediction. wood adhesive bond fracture mode II digital image correlation fracture energy les lepilni spoj lomni način II digitalna korelacija slik lomna energija true false true Angleški jezik Slovenski jezik Članek v reviji 2026-07-24 14:00:44 2026-07-24 14:00:55 2026-07-25 04:09:04 0000-00-00 00:00:00 2026 0 0 16 str. Vol. 84 iss. 4 2026 https://repozitorij.uni-lj.si/admin/GradivoOsnovno.php?id=185153 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 2026-01-01 630*843 1436-736X 10.1007/s00107-026-02447-9 285986051 straze_et_al.pdf straze_et_al.pdf 1 F3B7F39255329BAAF8ADB0AF1FD701E9 7d06f94965dbeec94ebd4d958cf91079273df7e2d7b44cd1ccfd8438c0321ad7 7b665a70-8757-11f1-9b0d-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=243381 https://link.springer.com/article/10.1007/s00107-026-02447-9 1 1614cb8b-8757-11f1-9b0d-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=243380 Biotehniška fakulteta 0 0 0