Wood is the most important and renewable source of energy which consists mainly of cellulose, hemicellulose, and lignin. Wood is an organic and a porous material. Being a natural composition of cellulose fibers embedded in lignin matrix makes wood extremely strong in tension and compression (the ability to resist compression). There are two types of wood commonly used: natural and engineered. Whereas Natural wood is harvested directly from natural growing trees, engineered wood is man made wood that has been manufactured to look like wood. It is made by binding or fixing the fibers harvested from natural wood together with adhesives such as glue. Despite the strength and stiffness that the wood holds, it is very necessary to conduct some tests on wood and timber. These tests are done in wood testing labs.
Why Testing of Wood is Done?
The use of wood is extensive in household and commercial sectors. Therefore before processing it into the final product, its strength should be analyzed. Flexure, tension and compression are the key parameters that should be focused upon while conducting a quality check. The testing enables us in analyzing the properties like performance, safety and quality of the sample in accordance with the guidelines set by the international standards. By determining the strength and deformation of the wood, it becomes easier to determine whether its fit for usage in manufacturing consumer goods such as children’s toy or a piece of furniture. Thus various tests are performed on wood in wood testing labs before carving it into the final product. For ex-the wood used in Japan should be flexible and elastic because of frequent earthquakes.
Tests assess the capability of the wood to handle stresses and strains when used in our daily life. Testing also helps the production lines to stick to pre-decided quality recommendations and helps to address the quality issues from customer’s side.
What Tests Determine the Quality of Wood?
Testing of wood is done to determine the strength of wood for various special applications. The objectives of the tests done in wood testing labs is to analyze the flexural and tensile strength, compressive strength, flexibility and grain structure of wood. Most of the wood that is used for the construction purposes (household or commercial), furniture manufacturing and other common products manufacturing industries are mechanically tested. These wooden and timber samples undergo a series of strength tests, on the basis of which its application for a particular purpose is analyzed. However, the nature of the test being conducted depends upon the purpose for which the tested sample is to be used.
Type of Tests.
Tests on wood can be divided into two categories.
- Destructive Tests
- Non Destructive Tests.
1. Destructive Tests
These tests require the specimen to be subjected to tests until its breaking point. Three major types of destructive tests are
- Tensile Strength tests-In this tests the wood specimen is pulled from both ends till the specimen breaks out. The reading of the load applied is noted down and at the break of specimen the load is marked as breaking point. This test is carried out on universal tensile testing machine.
- Compression test-Here instead of being pulled the specimen is pushed by load on its ends. The amount of load which causes fracture in middle is noted as compression breaking point. The load can be applied in two ways- parallel to grain structure or perpendicular to grain structure.
- Flexure Test-This is to determine the flexibility of the specimen. Here the load is applied at mid point with its two ends being supported .The more load the specimen can take the more it is flexible.
2. Non Destructive Tests
Here the specimen is not damaged and these tests are performed to determine the internal properties of the specimen.
- Visual Inspection-This is done with a naked eye or a magnifying glass to detect any visual cracks. Visual inspection is easy and cheap but has limitation like defects should be visible .
- Stress Waves-If the dimensions of the specimen are known then the internal decay in the specimen can be located. Stress waves propagate much slower through decayed wood than through sound wood. The common use of stress wave test is to determine the elasticity of the wood specimen.
- Ultrasonic- This test is used to locate internal cracks and structural faults in the specimen. Its added advantage is that it can be used for any size.
- Drill resistance-This is done to check the density and hardness of wood. The drilled hole may be sealed to prevent further decay.
- Vibrations- This is done to check the behavior of the specimen when subjected to vibrations. It gives an idea about the elasticity of the wood specimen.
Besides construction, wood is largely used in the manufacturing industry. Some typical applications for wood testing include Cork, Furniture, Laminated board, Plywood, Veneer sheets, Wooden containers.
Testing can make sure that the selected wooden resource should have the best features of a wood to manufacture the optimal product without quality and safety risks.
There are various wood testing labs conducting tests on wood. These labs specialize in destructive and non destructive testing. For proper testing a suitable equipment like universal testing machine or ultrasonic is required. Nowadays testing machines are making use of computers for better documentation and interpretation of results.