Bao et al. [2] conducted experiments to study the intrinsic differences in various wood properties between juvenile wood and mature wood in China. They also considered the differences in wood properties between plantation-grown juvenile and mature wood, and between naturally-grown juvenile wood and mature wood. Different tests, such as static bending for determining modulus of elasticity, as well as modulus of rupture, compression parallel to grain, tension parallel to grain, shear parallel to grain, cleavage parallel to grain and toughness were conducted in this study. Their test results compare for juvenile wood and mature wood in both plantation-and naturally-grown trees.
Kopac et al. [3] studied the machining of wood by cutting, which is a demanding technological process because of wood’s specific structure. Next, this study focused on the structural and mechanical properties of wood with outcome of the cutting process. Finally,
their work was intended to show the experimental results as regard to the wood strength in two different directions of wood cutting. The first is the differences between the modulus of elasticity and the strength characteristic on the grain orientation (three strengths:
compression, bending and tension). The second is that the hardness of wood had a major influence on the wood density and moisture content in three typical direction of wood tissue.
Oloyede et al. [4] measured the mechanical properties of wood in tension parallel to grain by for specimens prepared using three drying methods, ie. air-drying at ambient temperature, a conventional oven at two elevated temperatures and a microwave oven at two different power settings. Then, the results of the mechanical tests were compared for the various drying methods. The findings showed that microwave drying had reduced the strength of the dried timber compared with the strength when air-dried or dried in a conventional oven.
Edwin et al. [5] reported more than 3500 tests (green and drying condition) performed for seven strength and two physical properties. The wood samples (western juniper) were selected from 42 trees, and specimens were tested according to ASTM standard D-143-94. This work tried to explain the testing processes of static bending, compression, tension, shear, and hardness test and their application purpose. The strength values obtained for green and drying condition were compared with other wood from other areas, eg. Incense cedar, eastern and western red cedar, ponderosa pine and Douglas fir.
The strength properties of some commercially important woods grown in the United States are given in the Handbook-wood [6]. The strength values of sixty seven hardwoods and twenty nine softwoods, in static bending, impact bending, compression parallel to grain, compression perpendicular to grain, shear parallel to grain, tension perpendicular to grain and side hardness are recorded in this handbook. These values also indicate that some softwoods had greater strength than some hardwoods.
Josepf et al.[7] measured the strengths of some wood adhesives used in Cameroon.
This work carried out block shear tests to determine the shear strength of various types of adhesives selected in the Cameroonian market, according to ASTM standard D905-94.
The shear tests had been performed in four species of wood blocks such as Sadar glue, Ponal glue, Ebycoll glue and Bostik glue. The findings found that Sadar glue was more resistant than other three species.
Morrell et al. [8] focused on the testing of Norway spruce dried by two methods microwave drying and conventional air-drying. Their work was conducted to determine the strength of wood by using the three-point bending test. Wood specimens with a moisture content of 12% were tested. The findings found that the strength of wood had changed between specimens of the same species because of different structures for different purposes for its life. In addition, what affects wood strength was changeable such as moisture content, density, weight, width and thickness. Finally, the results showed the values of modulus of elasticity lie between 8.3 to 13 GPa and for modulus of rupture between 66 to 84 MPa.
Douglas et al. [9] focused on experimental shear strength research with three types of wood (green condition) and two other types of wood (air-drying condition).
Experiments were performed to determine their shear strengths. A three-point bending support investigated the effects of splits on shear strength and a five-point setup investigated the effects of drying on beam shear. Additional tests conducted on seasoned Douglas Fir and Southern Pine gave mixed results on the effects of splits. The test results showed that shear strengths ranged from 3.9 to 8.5 MPa for green condition and 7.4 to 12.7 MPa for air-drying condition.
Mattson et al. [10] focused on determining of wood properties related to drying methods of wood seasoning such as air drying method and kiln drying method. Seventy four types of wood were conducted to measure the specific gravity and shrinkage in volume, and seasoning characteristics. The woods used for the tests were not classified under hardwoods and softwood; instead, only local and family names were specified.
The above works attempt to describe the experimental test processes of wood for a number of different tests. In this research, the author will use the same test method and present the test results for seven species of Laotian wood. This research aims to conduct a similar study as the above-mentioned works in which only mechanical properties and physical characteristics were considered.