Agriculture Reference
In-Depth Information
LENGTH MEASUREMENT USING FIBRESHAPE
.
Fibre
or bundle fineness improves the tensile
properties of composites. As well as fibre
length, fineness is a decisive property for the
quality of injection-moulded parts. A modified
set-up has been developed for the image analy-
sis system 'Fibreshape' to measure the width
and length of fibres and fibre bundles extracted
from fibre-polypropylene (PP) compounds.
Measurement of fibre length and fineness
distribution was done by preparing the extracted
fibres as described above. The measured values
were used for the numerical simulation of injec-
tion-moulded flax/PP samples. With this
method, it is possible to show the differences in
fibre length reduction that result from using dif-
ferent compounding systems. Further details
have been published by Bos
et al
. (2006).
tive test by the Stelometer. This test requires
the sample to be conditioned for 24 h at
20°C and 65% relative humidity. Samples
were then clamped in a Pressley clamp
(Fig. 10.7) with Plexiglas jaws at a gauge
length of 3.2 mm. The Stelometer was
adjusted according to ASTM D 1445. To
obtain a representative set of results, more
than 20 collectives had to be tested. The
strength of fibre and fibre bundle collectives
in cN/tex could be calculated from the mass
of the bundle collective tested (kg) divided
by its mass-related fineness (tex). The mass
of the collective is measured with an accuracy
of 0.01 mg.
SINGLE
-
ELEMENT STRENGTH
/
DIA
-
STRON
.
The influ-
ence of fibre stiffness and the force elonga-
tion characteristics on composite behaviour is
clear. Reproducible methods are required for
the determination of the fibre properties pro-
viding data best suited to composite material
development (Müssig
et al
., 2005). According
to Nechwatal
et al
. (2003), the single-element
test is of particular importance in determin-
ing the tensile properties of fibres. Problems
in the implementation of such tests lie par-
ticularly in:
Strength
Tests for the tensile strength of hemp fibres are
not standardized and very different prepara-
tions and methods have been used in the litera-
ture. A comparison of the values found in the
literature is difficult, if not impossible, to under-
take. The different characteristics of hemp
fibre and fibre bundles used in tests are shown
in Fig. 10.6.
According to the N-FibreBase proposal
(Table 10.3), two methods were chosen to the
tensile properties. The collective test was use-
ful as a fast method to compare the quality of
fibres with nearly the same fineness. The sin-
gle-element test was chosen for testing the
exact mechanical properties.
•
the influence of the clamping mechanism
and of fibre slip in the clamp;
various gauge lengths and whether this
•
influence is taken into account;
the determination of the fibre or fibre bun-
•
dle cross-section surfaces;
calculation of the stiffness, e.g. Young's
•
modulus.
In order to solve the problems mentioned
above and to reduce the number of possible
influences on the testing result, an appropriate
testing instrument was obtained from Dia-
Stron Ltd, UK, and adapted to the require-
ments in an intensive exchange with this
company.
In this method, the individual elements to
be tested are no longer clamped but glued, in
order to reduce the influence of clamping, and
may be tested at gauge lengths of 30, 20, 10,
5 and 3.2 mm. The compliance of the system,
99% of which is due to the load cell, is corrected
directly in the analysis. The cross-sectional
surface area of each element is measured by
COLLECTIVE STRENGTH
/
STELOMETER
.
The differ-
ent samples were measured with the collec-
Hemp
single
fibre
Hemp
single fibre
collective
Hemp
fibre bundle
Hemp
fibre bundle
collective
Fig. 10.6.
Various forms of hemp fibres
(Müssig, 2001a).
