Agriculture Reference
In-Depth Information
Harvesting, mechanical separation
close coordination with the working group on
natural fibre reinforced polymers of the
German Federation for Composite Materials
(AVK-TV).
Harvesting parameters play an important role
for further processing steps by the compounder
or the needle felt manufacturer. A high
proportion of wooden stem parts, for exam-
ple, can interrupt processing and can also cre-
ate mechanical weak points in the component.
With an optimum retting time, the relationship
between fibre strength and fibre fineness
(as regards the transmission of forces between
the matrix and the fibres) can be improved.
This also optimizes the mechanical properties
of the finished part.
Fineness
According to the detailed analysis of possible
fineness measurement methods suitable for
very different natural fibres, we decided to
concentrate on two methods. Both these
methods have also been favoured by the
N-FibreBase proposal (
www.n-fibrebase.net)
and AVK-TV group. In the following, the
gravimetric fineness measurement method
and the image analysis system,
Fibreshape
, in
combination with a high-resolution scanner
will be described in detail.
10.2.2 Suitability of the
measurement method
In the course of history, different measuring
systems and testing specifications for cot-
ton, wool, bast fibres and synthetic fibres
have come into use in the textile industry.
Each method has been developed to deter-
mine the morphological properties of one
kind of fibre. Thus, it cannot simply be
applied to other fibres. We have carried out
an evaluation of the present measuring
methods with regard to their usability for
quality control in mass production, compris-
ing the following topics:
GRAVIMETRIC FINENESS MEASUREMENT
.
After
24 h of conditioning (20°C, 65% relative
humidity of air), the fibres and fibre bundles
are combed very softly without losing fibres
on any of the two sides of the prepared sam-
ple. Very important for this preparation step
is not to separate the bundles into finer bun-
dles. After this preparation, the sample is cut
to a length of 20 mm. The fibres are sepa-
rated using tweezers. Each fibre or fibre bun-
dle with a length of 20 mm is counted and
stored for subsequent weighing of the com-
plete samples. For each sample, 500 fibres or
fibre bundles are counted and weighed. The
gravimetric fineness
gF
in tex is calculated by
using the following equation:
•
objectiveness
•
suitability for incoming control tests and/
or numerical simulation of properties
flexibility and comparability of the results
•
•
economic aspects like cost per measure-
ment or cost of the testing device.
M
mg
Care has been taken to recommend only
flexible methods that are in widespread use.
Table 10.2 gives an overview of the methods
evaluated.
-
3
6
gF
=
×
10
·10
l
=
1000
N
×
B
B
mm
where
N
B
is the number of counted fibres,
M
the mass of the collected fibres in mg and
l
B
the length of the cut fibres in mm (here
20 mm).
10.2.3 Recommended methods
As an orientation aid for industry in selecting
test methods, recommendations have been set
up as part of the N-FibreBase project:
www.n-
fibrebase.net.
These test recommendations are
listed in Table 10.3. They were developed in
FIBRE WIDTH DISTRIBUTION WITH FIBRESHAPE
.
Fibre
fineness is an important fibre property because
it describes the quality of the separation
process. An image analysis system called
