Enhancing strength of the mortise and tenon joints with densified wood

In this study, it was aimed to present a value-added material made of densified cottonwood, which is not preferred due to its low strength by densifying wood material. For this purpose, cottonwood was densified at the rates of 10, 20 and 30% via the surface densification method, and their modulus of rupture (MOR), modulus of elasticity (MOE), and parallel to grain compression strength (CS) were compared to hornbeam wood which mainly used in furniture frame constructions. Besides, the bending moment capacities of the T-shaped mortise&tenon (MT) and domino joints made of hornbeam and cottonwood were benchmarked. Hornbeam, cottonwood, and densified cottonwood were used in the domino joint. Results showed that MOR and MOE of the hornbeam were 100,82 N/mm2 and 11211,22 N/mm2, while those of Cottonwood were 56,22 N/mm2 and 5775,65 N/mm2, respectively. In the case of densification rate was 10%, MOR and MOE were 67,58 N/mm2 and 7906,07 N/mm2. Those of 20% and 30% were 74,90 N/mm2 and 7837,47 N/mm2, and 66,64 N/mm2 and 7043,28 N/mm2, respectively. CS of the hornbeam was 52,45 N/mm2, while those of cottonwood was 29,30 N/mm2. In the case of densification rate was 10%, 20%, and 30%, CS values were 32,75 N/mm2, 38,19 N/mm2, and 43,17 N/mm2, respectively. The effect of the densification was observed at most for the rate of 20% in MOR and MOE and 30% for CS. Even though densification increased material strength, they were still lower than some mechanical properties of hornbeam. The bending moment capacity of the T-shaped MT joints made of hornbeam (259,49 N.m) wast the highest, and those of domino joints made of hornbeam (194,53 N.m) followed it. The effect of the densification was observed in domino joints made of Cottonwood with a rate of 20% densification (186,19 N.m). It had a higher bending moment capacity than T-shaped MT joints made of cottonwood (175,56 N.m). In conclusion, results showed that the rate of 20% densification was appropriate for solid wood and furniture joints. However, they were lower than those of hornbeam. Albeit, there is no statistically significant difference between the bending moment capacity of the domino joints made of Cottonwood with the rate of 20% densification and hornbeam. Therefore, it can be said that the findings of the study were successful, and densification could increase the strength of the furniture joints. Keywords: Densified wood, T-shaped furniture joints, Domino, Mortise&tenon, Mechanical properties of wood, Furniture mechanics