Strip-Like Laminations Influence on Bending and Bonding Performance of Yellow Birch Glulam

Abstract

Strip-like laminations are wood lamellae formed by face-gluing small wood segments to reduce the effect of natural defects and enable the use of lower-grade timber. This technique offers a promising solution for transforming low-grade wood into solid products. However, its impact on full-scale structural components such as glulam beams has yet to be thoroughly assessed. This study investigated how external layers made of strip-like laminations affected glulam’s bending properties and bonding performance. Grade No. 2 yellow birch (Betula alleghaniensis Britt.) was bonded with one-component polyurethane to fabricate six-layer glulam beams, with strip-like laminations placed on the outer layers. Mechanical testing, including four-point bending, block shear, and delamination, was conducted in accordance with North American standards. Results showed a one-third reduction in the variability of modulus of rupture (MOR), while maintaining comparable performance to traditional glulam configurations. Although apparent modulus of elasticity (MOE_app) was slightly lower and similar to beams containing visual defects, block-shear strength exceeded 90% approval. Some cases of delamination above 10% highlight opportunities for process refinement. These findings demonstrate the potential of strip-like laminations for improving material utilization and provide valuable insights for optimizing manufacturing strategies.