Investigation Properties and Dimensional Stability of Thinned Teak (Tectona grandis)

Abstract

In this study, the mechanical properties and dimensional stability of thinning teak plantations which were 15 and 25 years old were examined. Teak trees were selected from the Forest Industry Organization located in Kanchaburi, Thailand. The specific gravity, moisture content, density,swelling and shrinkage of radial, tangential, and volumetric were measured. The mechanical properties were tested to determine the static bending, compression parallel and perpendicular to the grain, shear strength parallel to grain and hardness according to the ISO standard. Specimens were tested at three different positions, i.e., bottom, middle, and top of each position 120 cm in length and nested designs were used for the analysis of variance. The results were compared to the strength of sampled wood from various positions. The results indicate that mechanical properties of 15 years old thinned teak were higher than 25 years old. Most properties were not statistically significant apart from the compression perpendicular to the grain and tangential section hardness. The strength of each position was statistically significant. The average strength of thinned 15 years old teak was ordered as being
from the bottom, middle to the top of the stem. The densities were 655.86, 627.25, and 622.25 kg/m3 while the specific gravities were 0.59, 0.56. and 0.55, respectively. Mechanical properties such as modulus of rupture were 149.98, 139.33 and 132.87 MPa, modulus of elasticities were 12775.85, 12618.70 and 11857.68 MPa, compression parallel to the grain were 63.92, 62.95 and 61.17 MPa, compression perpendicular to the grain were 33.97, 26.46 and 26.40 MPa and the shears strength were 12.79, 11.36 and 9.84 MPa. Meanwhile the longitudinal hardness were 6.50, 6.14 and 6.05 kN, tangential hardness were 6.76, 6.34, and 5.90 kN, while the radial hardness were 5.35, 5.49 and 5.11 kN, respectively. The average strength of the 25 years old thinned teak was ordered as being from the bottom, middle to the top of the stem. The densities were 617.88,584.48 and 570.14 kg/m3, specific gravities of the oven dry weight were 0.54, 0.52 and 0.53, the mechanical properties such as modulus of rupture were 133.68, 131.21 and 125.36 MPa, modulus of elasticities were 13180.90, 13089.71 and 13825.30 MPa, compression parallel to the grain were 61.63, 59.96 and 58.97 MPa, compression perpendicular to the grain were 24.32, 21.96 and 21.22 MPa and shear strengths were 11.43, 10.67, and 10.25 MPa. Meanwhile the longitudinal hardness were 5.63, 4.73 and 4.46 kN, tangential hardness were 6.18, 4.87 and 4.08 kN, while
the radial hardness were 5.21, 4.01 and 3.48 kN, respectively. The strengths of wood decreased with increasing positions and were statistically significant except for the compression parallel to grain. The dimensional stability of 15 years old thinned teak was ordered as being from the bottom, middle, to the top of the stem. It was found that the radial swellings were 2.91%, 2.94% and 3.10%, tangential swellings were 4.41%, 4.80% and 6.10%, while the volumetric swellings were 7.46%, 8.05% and 9.20%. The radial shrinkages were 2.83%, 2.85% and 3.00%, tangential shrinkages were 4.22%, 4.57% and 5.72%, while the volumetric shrinkages were 6.93%, 7.44%and 8.42%, respectively. The dimensional stability of the 25 years old thinned teak was ordered as being from the bottom, middle to the top of the stem. The radial swelling s were 3.01%, 3.14% and 3.25%, tangential swellings were 4.84%, 5.52% and 5.79%, while the volumetric swellings were 8.00%, 8.83%, and 9.24%. The radial shrinkages were 2.92%, 3.04%, and 3.15%, tangential shrinkages were 4.62%, 5.22% and 5.47%, while the volumetric shrinkages were 7.40%, 8.10% and 8.44% respectively. Moreover, the dimensional stabilities of the 15 and 25 years old thinned teak were not significantly different and decreased with the stem height.