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Tensile Strength of Plant fibres

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					The Strength of Plant Fibres

Nishat Karim

Plant fibres are a range of ‘fibre-like’ structures that include long, stretched, thick and
lignified cell walled tubes which can be used for different purposes depending on their
properties such as linen and cotton for clothing, ropes, sacking, paper and cardboard. The
cell wall of the plant fibres made up of a net-like arrangement of cellulose microfribils which
strengthens to the plant fibres. Sclerenchyma fibres that are present in plant fibres form
secondary cell wall which are dead cells with lignin which strengthen the plant fibres even
more. The xylem and phloem are also responsible for plant fibres’ thick cell wall and
hardness due to the lignin on the outer part of their vessels.

Aim: To find out the tensile strength of plant fibre this is a measure of the force required to
pull something such as the fibres to the point where it breaks, this is to find out how well the
fibres do their function in supporting the plant and withstanding forces applied which help
protect the plant.

Hypothesis:
I believe that the tensile strength of the flax fibres will very much depending on how thick
and healthy the sample is. I reckon that the fibres will have a high tensile strength, however it
is difficult to investigate 100% fairly.

Independent Variables:

The variable which will always remain unchanged is the source and type of fibre used

Dependent variables: We will be measuring the amount of mass the flax fibres can hold till
it breaks.

Control variables: in order to get accurate results I would have to control numerous factors
such as the thickness of each plant fibre, length of each plant fibre, the way the mass was
hung for each plant fibre and the temperature/humidity of the room as these all can affect
the tensile strength leading to inaccurate results.
Apparatus:

         Scalpel
         Forceps
         Flax
         Clamps and clamp stands
         Mass (10g) and mass holders
         White tile
         Methylated sprit

Safety:
Weights can be hazardous as if it bounces of the workplace it can land on the foot and cause
injury therefore to avoid this pay attention to the masses or place some soft material onto
the clamp stand to prevent the bouncing off the masses, also when using the scalpel cut
away from yourself to avoid cutting yourself.

Method:

we used a method called retting to extract the plant fibres from the flax plant this is by using
the scalpel, place the flax onto the white tile and scrap the upper layer of the woody core
(xylem) and the epidermis to see the fibre’s, use the forceps to take out the separate fibres
from the flax, try to get the longest length possible and get about 5 of each plant, in our
case we only had 5 fibres of the flax plant. We then connected the fibre onto 2 clamp stands
horizontally and then added a mass holder and then added mass until the flax fibre snapped.
We wanted to try out different ways of combining fibres by twisting and plaiting to see the
effect on tensile strength.

Results:

Plant          Tensile strength (g)
fibres
1              60
2              20
3              50
4              30
5              10
Mean           34


Evaluation:

Looking at my results we could see that the plant fibres can hold some sort of mass
therefore the tensile strength is averagely good however as we weren’t able to plait/twist the
fibres due to lack of time we couldn’t see the effect of using may fibres to gain extra tensile
strength as this is the method industrials use for clothing and making ropes etc.

Issues:

We came across many issues that could have effect the reliability therefore the validity and
also precision, we could have tried to minimise the systematic, human and random errors, we
were unable to use the same length plant fibres which highly effects the reliability of the
results When using the clamps the fibres weren’t staying on the clamp and this could have
affected the mass added because it may have just came off the clamp rather than snapping
e.g. On plant fibre 5.also we used different methods in ensuring that the fibres would stay on
the clamp. Random error can also been the reason for the anomaly results an example of this
is tiredness of trying to get the fibres to stay on. Also, as time was limited many of the
recorded results may have been rushed. As a result of this, the accuracy of the results may
have been affected

				
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Description: My Biology AS core practicals writeup to help you :D