Nodal Defects and Their Influence on Wave Propagation in Juvenile Wood of Tectona grandis

Abstract

Acoustics plays a significant role in the classification of a wide range of products in wood science and technology, from standing trees to structural elements. The study of wood acoustics involves the use of mechanical waves that are sensitive to several factors, including sample dimensions, intrinsic characteristics of the wood species, and the presence of defects. This study aimed to estimate the modulus of elasticity in juvenile wood of Tectona grandis using three different non-destructive wave-based evaluation methods: ultrasound, impulse vibration, and stress waves, with the goal of identifying the most suitable technique for predicting this mechanical property. Additionally, the study evaluated the impact of knots on wave propagation velocity and, consequently, on the estimation of the modulus of elasticity. Specimens measuring 20 × 20 × 300 mm (width, thickness, and length, respectively) were used, totaling 42 samples divided into two groups: with knots and without knots. The results indicated that all evaluated methods were effective and exhibited strong correlations with the estimated modulus of elasticity. Furthermore, the presence of knots in young, fast-growing teak wood did not significantly influence wave propagation.