JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 51

One of the most critical points to ensure
reproducible results in a micro-bond
test is the precise embedding of the
fibre, which is required to avoid bending
forces. For this purpose, the fibre has
to be embedded exactly at the centre of
the matrix droplet. In the final version
of the embedding station, the critical
adjustment process ensuring this will be
controlled by an image analysis software
program developed by FIBRE.

Fig. 3: (left) Textechno's new FIMABOND device for embedding the fibre in the matrix and (right) the pull-out
device to be installed in Textechno's FAVIMAT+

extensively discussed in the literature,
and it has been found that, for many
fibre/matrix systems, interfacial failure
can be satisfactorily described using
either one of these criteria.
Although these tests are experimentally
simple, the question of proper bond
strength determination to obtain a specific numerical value remains rather ambiguous. At least eight different approaches
to bond strength determination have
been proposed, which can be classified
according to the following alternative
features:
- averaged/local (determination of the
"apparent" or local interfacial shear
strength (IFSS));
- stress-based/energy-based (adhesion
strength parameter and failure criterion
local IFSS, τd, or critical energy release
rate, Gic);
- direct/indirect (adhesion strength
determined from individual force-displacement curves or estimated from the
data obtained for a set of specimens).
Since a theoretical comparison of different approaches is ongoing elsewhere,
it seems interesting to compare these
methods using reliable experimental
data. A key feature is the preparation of
single-fibre model composites.

New pull-out test system
The performance of composite materials strongly depends on the adhesion
strength between fibre and matrix. At
the microscopic level, different test
procedures have been established by
various research institutes. However,
most results are not comparable since
none of these tests is standardized or the
equipment is not commercially available.
In order to make a versatile and reproducible single-fibre pull-out test available
to institutes and industrial customers
worldwide, Textechno, leading experts
in the field of fibre testing, are developing a suitable system together with the
Leibniz-Institut für Polymerforschung
Dresden (IPF) and the Faserinstitut Bremen (FIBRE). While the IPF
has long-standing competence and
experience in the field of fibre/matrix
adhesion strength, FIBRE contributes
by its experience in image analysis.
The system consists of two devices:
the FIMABOND partially automated
embedding station, which is suitable
for all types of reinforcement fibres as
well as for thermoset, thermoplastic
or mineral matrices, and a device that
performs high-precision pull-out tests as
a new accessory to Textechno's singlefibre linear-density and tensile tester,
FAVIMAT+.

The integration of the pull-out testing
device into Textechno's FAVIMAT+
saves money for the user since this versatile single-fibre tester fulfils the requirements with its high-resolution load cell
(1µN at 200 cN full range) and highly
precise and sturdy mechanics. The
integrated linear density test allows easy
and precise determination of the linear
density, cross section, modulus, breaking
strength and elongation (in combination
with the tensile test). A microscopic
camera facilitates the adjustment of
the clamps as close as possible to the
matrix surface with perfect alignment.
The complete set-up, called FIMATEST,
consists of the FIMABOND embedding
station and the FAVIMAT+ tensile and
pull-out tester. The new system will be
exhibited at JEC World 2016. n
References
[1] Mäder, E.; Moos, E; Karger-Kocsis,
J. Role of ﬁlm formers in glass ﬁbre
reinforced polypropylene - new insights
and relation to mechanical properties.
Composites A 32 (2001) 631-639.
[2] Zhandarov, S.; Mäder, E. Characterization of ﬁber/matrix interface strength:
applicability of different tests, approaches and parameters. Compos Sci Technol
2005; 65: 149-60.
[3] Mäder, E.; Gao, SL.; Plonka, R. Static
and dynamic properties of single and
multi-ﬁber/epoxy composites modiﬁed by sizings. Compos Sci Technol 67
(2007) 1105-1115

No102 January - February 2016 / jec

More information:
www.textechno.com
www.amac-international.com
www.ipfdd.de

composites magazine 51

http://www.textechno.com http://www.amac-international.com http://www.ipfdd.de

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016