PSI - Issue 51

Zahra Silvayeh et al. / Procedia Structural Integrity 51 (2023) 141–144 Z. Silvayeh et al. / Structural Integrity Procedia 00 (2023) 000–000

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1. Introduction To reduce fuel consumption and thus to decrease CO 2 emissions the automotive industry is shedding the weight of vehicles powered by internal combustion engines wherever possible. Taub et al. (2019) remarked that even light weighting of modern battery electric vehicles is of utmost interest for compensating the lower energy density of batteries compared to liquid fuels. In particular wood-based materials offer great technological, economical and eco logical potentials for automotive lightweight applications. As reviewed by Kohl et al. (2016), wood can be used not only for design components, but also for load-bearing structural components. Baumann et al. (2019, 2020) demonstrated that a wood-based side impact beam, which can be installed inside the door of a passenger car, possessed similar energy absorption under high static and dynamic loads as a comparable steel beam. As the numerical dimensioning of components and structures has become increasingly important, Müller et al. (2020) presented a material model for the use in finite element (FE) simulations of crash-relevant wood components in future car bodies. Introducing wood-based materials in multi-material car bodies requires capable and reliable technologies for dissimilar joining or bonding. Riv-bonding, which combines self-piercing riveting (SPR) and adhesive bonding, has been established as standard technology for joining similar and dissimilar metals such as aluminum alloys (Domitner et al. (2022b), Potgorschek et al. (2020)), aluminum alloys with high-strength steels (Domitner et al. (2022a)), alu minum alloys with magnesium alloys (Domitner et al. (2022c, 2023a)). The feasibility of classical riv-bonding for dissimilar joining of wood with metals has not been proven yet; however, the feasibility of screw-bonding, which combines mechanical fastening using screws and adhesive bonding, has been verified. Imakawa et al. (2022) studied screw-bonding of spruce-pine-fir (SPF) blocks with 2.3 mm-thick steel sheets, and Domitner et al. (2023b) investigated screw-bonding of 9 mm-/13 mm-thick cross-laminated birch veneer plates with 1.5 mm-thick aluminum alloy sheets. Based on the results they showed potentials for the optimization of hybrid screw-bonded joints. Because of their more uniform properties parts of cross-laminated wood veneers are more suitable for automotive applications than parts of solid wood. Therefore, this prestudy focuses on the static strength of hybrid screw-bonded lap joints of 4.5 mm-thick plates consisting of three 1.5 mm-thick cross-laminated beech veneers and 1 mm-thick sheets of EN AW-6016-T4 aluminum alloy. The influence of the stacking order of the veneers was also considered. 2. Materials and methods Commercial 1 mm-thick EN AW-6016-T4 aluminum alloy sheets were screw-bonded with 4.5 mm-thick veneer plates using two standard ST4.8×16 pan head drilling screws with tapping screw thread and drill tip, as well as about 0.5 g (280 g/m 2 ) of commercial liquid single-component polyurethane-(PU)-based adhesive The adhesive was partly squeezed out of the joining gap. Total length, total width and overlapping length of the screw-bonded samples were approx. 180 mm, 90 mm and 20 mm, respectively, and the distance between the screw axes was 45 mm. Plates with cover veneers oriented either longitudinal (L) or transverse (T) to the uniaxial loading direction and with stacking orders designated as L/T/L and T/L/T were used for preparing the samples. Fig. 1 shows exemplarily the cross-section of a screw-bonded joint with veneers in T/L/T stacking order at the scale of 1:1.

Fig. 1. Cross-section of a screw-bonded joint consisting of an aluminum alloy sheet and of a beech veneer plate in T/L/T stacking order, with fibers oriented parallel (dark brown) and transverse (light brown) to the load direction.

A spindle-driven Zwick/Roell Z100 uniaxial testing machine with a 100 kN-load cell and mechanical clamping jaws as shown in Fig. 2 (a) was used for quasi-static shear-tensile testing of the screw-bonded samples. The testing speed was 5 mm/min. The tensile force-displacement curve was monitored during each of the tests.