Plant Fibre

Experiment to investigate the tensile strength of fibre

Introduction Plant fibres are long, stretched, thick and lignified cell walled tubes. One component of the plant fibre is its cell wall made of cellulose microfribils in a net-like arrangement which gives strength to the plant fibres. Slerenchyma fibres are also present in plant fibres. They form secondary cell wall which are dead cell with lignin which provides even more strength to plant fibres. The xylem and phloem are also responsible for plant fibres’ thick cell wall and hardness. This is because the lignin on the outer part of their vessels. Retting is a stage in the manufacturing of vegetable fibres, especially the bast fibres. It is a process that employs water and microbial action to separate the bast fibres from the woody core (the xylem), and sometimes from the epidermis as well. Retting can be done by letting the cut crop stand in the fields in the wet Fall, called "dew retting". Bacterial action attacks pectin and lignin, freeing the cellulose fibres. The stems are monitored during retting to avoid excessive degradation of the fibres, making it a very labour-intensive process. The stems can now be removed and processed mechanically to produce fibres. These fibres can be tested to measure the amount of tensile stress it can cope before it breaks. This is known as tensile strength. Knowing the tensile strength of a fibre can make it suitable for different uses. E.g. ropes for climbing have to have a certain amount of stress tolerant for it to be suitable to carry a person. Equipment ➢ Fibre ➢ clamp ➢ clamp stand ➢ bulldog clips ➢ weights ➢ Method ➢ Attach the clamp to a clamp stand with the clamp stand places vertically on a table. ➢ Take the measurement of a fibre (diameter) with a before inserting it into the clamp. ➢ Attach a bull dog clip to the other end of the fibre where the weights can be gradually added on until it breaks. ➢ Record the mass needed to break the fibre ➢ Repeat the experiment with different sample of the same fibre ➢ The fibres being tested should be the same length

Result Nicholas Itam

Diameter (mm) Before breakage After breakage

1.31

1.22

1.29

Average 1.42 1.27

Weight (g) required before breakage: 1690 Mass (g) x 9.81

Analysis Tensile strength (NM ) = Max force (N) Cross sectional area(M ) = 1690 x 9.81 π x (1.27÷2)2

πr2

= 13086NM Question Extracted fibres are very strong as you can see form my above result; it has a tensile strength of 13086NM which mean it can withstand a lot of stress. This ability for it to withstand stress makes them suitable in making robe. Fibres are stronger than an intact stem as they are flexible which avoid them from breaking easily, instead they will rather stretch, unlike an intact stem that will snap as it has less flexibility. Using my result, fibre is not stronger than concrete which have a tensile strength of 2x10^6, however modified fibre like carbon fibres are more stronger with better tensile and flexural properties, toughness, and durability than concrete.

Nicholas Itam