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Effect of Age and Height Position of Muli (melocanna Baccifera) and Borak (bambusa Balcooa) Bamboos on Their Physical and Mechanical Properties.

M. A. Sattar
Director (Ex.)
Seasoning and Timber Physics Division, Bangladesh Forest Research Institute, Chittagong.

D.K. Bhattacharjee
Seasoning and Timber Physics Division, Bangladesh Forest Research Institute, Chittagong.

M.F. Kabir
Research Officer
Seasoning and Timber Physics Division, Bangladesh Forest Research Institute, Chittagong.

Abstract/ Executive Summary:

The physical and mechanical properties of one year to five years old muli and borak bamboo have been studied. The moisture content and the shrinkage change significantly along the culm height. The age has substantial effect on these properties for borak, but not for muli. Specific gravity differs considerably with height and age. Mechanical properties have also changed with age and height position. Both the species have been found to attain maturity in respect of specific gravity and bending strength at the age of three years.

Keywords: Physical and mechanical properties, Muli, Borak, Age,Height position,

Location: Bangladesh Forest Research Institute, Chittagong. Baorak bamboos were procured from a village grove of Chittagong.

Start Date: 00-00-0000

End Date: 00-00-0000

Program Area: Conservation and Biodiversity

Commodity: Bamboo

Objectives:

To find out the properties which help in the proper use of bamboos.

Methodology:

Muli bamboo were collected from the bambusetum of the Bangladesh Forest Research Institute, Chittagong. Baorak bamboos were procured from a village grove of Chittagong. Five age groups, from one year culm to five years culm, were taken for each species. Three height positions –butt, middle and top of the culm were also considered for each investigation. Five bamboos were used for each age group for replication of tests.

.Shrinkage: The specimens for wall-thickness shrinkage were prepared in the form of 2.5 cm wide rings while the specimens for diameter shrinkage were the internodes of the culm bounded by nodes at the extremity. A total of three rings and three internodal culms were cut from the butt. middle and top of each bamboo. The green wall thickness was determined at two perpendicularly marked positions and the diameter shrinkage was measured along the two diameters perpendicular to each other. The specimens were first dried to about 12% moisture content and then the wall thickness specimens were dried gradually from 60⁰C to finally 103 ± 2⁰C. The shrinkages were calculated at 12% mc and ovendry condition based on green dimension.

Moisture content and specific gravity: The specimens for moisture content and specific gravity were taken in the form of a pair of 2.5 cm rings from each of the height positions. Moisture content was determined in green condition and then ovendrying them. The specific gravity was determined on the basis of both green and ovendry volumes. The initial volume was taken in green condition and the specimens were ovendried, weighed, soaked in melted paraffin, and ovendry volume was determined. In both the cases, the volume was ascertained by the water displacement method.

Mechanical properties: There is no universal standard method of tests for evaluation the mechanical properties of bamboos. Different countries, however, have standardized some specifications to suit their purposes. In the present study the Indian method was followed.The static bending test was performed on full diameter specimen of 75 cm length bounded by two nodes. Paired specimens were prepared for each height position. The half of the number of the specimens was tested in green condition and the other half was tested in air dry condition at about 12% mc. The modulus of rupture and modulus of elasticity were evaluated from this test.The compression parallel to grain test was made on full diameter specimens without any node. The length of the specimen was taken 10 times the average wall thickness of the culm. Paired specimens were prepared from the butt, middle and top of each bamboo. The specimens were tested in green and air dry conditions on a timber testing machine with a platen equipped with a hemispherical bearing to obtain uniform distortion of load over the ends of the specimens. The maximum compressive strength parallel to grain was determined from this test.

Source of Information: Bangladesh Journal of Forest Science, Vol :19 (1 & 2), Jan-July 1990, 29-38

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The moisture content and shrinkage of muli (Melocanna baccifera) and borak (Bambusa balcooa) were significantly affected by the height of the culm. The age has a substantial effect on these physical properties for borak, but not for muli.The specific gravity differed significantly with the height and age. It attained the highest value at the age of 3 years for both the species. The top was found to be the most dense in all cases.Mechanical properties, viz., modulus of rupture, modulus of elasticity and compressive strength were also affected by the height and age. Both the species were observed to attain maturity in respect of bending strength at 3 years. The 4-year old muli showed the maximum compressive strength while this property was maximum at the age of 3 years for borak.

Knowledge Management: Journal