Abstract
This study aimed to examine the in-plane shear and out-of-plane shear strength characteristics of single-layer and two-layer extrusion-based additive manufactured timber beams made from wood fibers and sodium silicate, which will be defined hereafter as Printimber. The beams were tested for in-plane shear using the modified plate shear (MPS) test according to ASTM D2718, and for out-of-plane shear using short-span bending (SSB) tests in accordance with ASTM D198. This study examined the effect of different loading angles (0°, 5°, and 14°) on the in-plane shear performance of Printimber beams and compared the in-plane shear and out-of-plane shear strength characteristics of 3D single-layer and two-layer specimens. The results indicated that as the loading angle increased, the load-carrying capacity and in-plane shear modulus of single-layer specimens decreased. However, the two-layer specimens showed consistent performance regardless of the loading angle. The findings revealed that single-layer specimens demonstrated a 6% higher in-plane shear modulus than two-layer specimens at a 0° angle. However, at 5° and 14° angles, the in-plane shear modulus of single-layer specimens was 8.7% and 20.6% lower, respectively. Both types of specimens exhibited a decrease in in-plane shear strength as the loading angles increased, with a more pronounced decline observed in single-layer specimens. There was a disparity in comparison of median in-plane and out-of-plane shear strength values of single-layer specimens. The failure patterns differed according to the type of specimen and the angle at which it was loaded. Single-layer specimens exhibited cracks of moderate thickness, while the two-layer specimens failed by debonding at the layers’ interface. The findings emphasized the critical role of loading angles in the structural behavior of PrinTimber beams and provided valuable insights for their design and use in sustainable construction. Results further demonstrate that PrinTimber delivers promising shear performance for structural applications, underscoring its potential as an innovative timber composite, while large-scale and long-term studies remain necessary before adoption in primary load-bearing structures.