PSI - Issue 77

Eva Graf et al. / Procedia Structural Integrity 77 (2026) 331–338 Graf et al. / Structural Integrity Procedia 00 (2026) 000–000

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Even without mechanical surface pretreatment of the aluminum alloy and the plywood, debonding between both materials was negligible for PF- and PUR-bonded samples, as illustrated in Figure 4 (a). Sporadic minor fiber buckling in the compression zone of PF-bonded composites caused local debonding of the veneers, although it did not impair the load-bearing capacity of the composite. In contrast, EP-bonded composites failed abruptly after reaching the maximum bending force due to debonding at the aluminum-wood interface, as illustrated in Figure 4 (b). In general, decreasing the thickness of veneers increases the mechanical properties (e.g., tensile strength) of plywood, which is due to a reduction of the lathe check depth during veneer manufacturing, which affects the mechanical strength of plywood (Pramreiter et al., 2021) (Rohumaa et al., 2013). The bending strength of aluminum-wood composites made of 0.5 mm-thick veneers in this study was found to be similar to that of composites using 1 mm-thick veneers, which were previously reported to have a bending strength of 128 MPa (Graf et al., 2025). In general, the bending strength of aluminum-wood composites exceeds the bending strength of common plywood products (30-35 MPa) and of LVL (60-100 MPa) (Huang et al., 2024).

Fig. 4. Microscope images captured after quasi-static three-point bending of (a) PF-bonded, and (b) EP-bonded aluminum-wood composites in L-stacked configuration.

3.2. Impact bending Figure 5 (a-d) shows the bending force-displacement curves obtained from evaluating the measuring signal, and Figure 5 (e) shows the impact energy absorptions and bending strengths.

Fig. 5. (a-d) Examples of bending force-displacement curves and (e) energy uptake and bending strength of impact tests for (a,b,c) aluminum wood composites adhesive-bonded with (a) PF, (b) PUR, and (c) EP, and for (d) 2 mm- and 4 mm-thick aluminum alloy sheets. P and L refer to the perpendicular and longitudinal stacking order, and Inv. refers to inverted loading direction (i.e., aluminum alloy on the impacted side). Sample configurations were only tested once. Compared with the bending strength determined in quasi-static bending, the bending strength under impact bending was about 10 % lower. This suggests that the debonding in the forming zone may outweighed the strain-rate sensitivity