Final report
Dates and location
20 March — 22 March 2017, Tallinn, Estonia
Chairperson
Heiko Herrmann
Co-chairperson
Jürgen Schnell
Conference fees
- Regular Registration Fee: 200.00 €
- Late Registration Fee: 250.00 €
- Late Registration Fee PhD Students: 200.00 €
- Regular Registration Fee PhD Students: 150.00 €
What other funding was obtained?
Support in kind by Tallinn University of Technology (TTU), TTU Mektory and from PUT grant 1146
What were the participants offered?
Conference bags containing book of abstracts, pen, paper, maps, name badge; coffee breaks inclusive coffee, tea & snacks; registration reception; conference banquet (Monday), dinner (Tuesday); lunch on Wednesday; walking tour through Tallinn Old Town with guide (Monday)
Applicants (members)
- Heiko Herrmann
- Akke Suiker
Applicants (non members)
- Valentin Antonovič
- Wilfried Becker
- Renata Boris
- Andres Braunbrück
- Daniele Casucci
- Prakash Easwaran
- Marika Eik
- Oksana Goidyk
- Klaus Holschemacher
- Andrejs Krasnikovs
- Arturs Lukasenoks
- Jesús Mínguez-Algarra
- Tyler Oesch
- Alexander Ryabchikov
- Johan L. Silfwerbrand
- Tanel Tuisk
- Miguel A. Vicente
Scientific report
Composites containing short fibers are important in many technological fields, the used composites range from fiber plastics to fiber concretes. Especially in the building industry fiber composites are gaining importance, as they may increase the building speed and improve material properties. The used fibers include steel, basalt, carbon and polymer fibers, of many different shapes and aspect ratios. The target of including fibers also differs, including improving tensile strength, postcracking behaviour (ductility) and temperature resistance. In all cases, the microstructure and spatial and orientational distribution of the fibers is important. At this colloquium different methods and results for the analysis of microstructure and fiber orientation analysis in cementitious building materials containing fibers, among them concretes and refractory composites, have been presented.
The goal of the colloquium was to present a platform for the exchange of ideas between different fields with simular problems. While having different chemical composition and length scales, cementitious composited and ceramics reinforced with short fibers share similar mechanical properties and theoretical problems. Especially the addition of the short fibers makes the composite stochastically anisotropic and inhomogeneous, since several macro- and meso-scale properties depend on the spatial and orientational distribution of fibers. An important aspect is the micro-structure around the fibers and the adhesion of the matrix to the fibers, which has large influence on mechanical properites.
There were altogether 19 participants and 14 presentations, among these 3 keynote talks, given by Daniele Casucci (Kaiserslautern), Johan L. Silfwerbrand (Stockholm) and Akke Suiker (Eindhoven); see also the list of participants and programme. Most importantly, the length of the presentation slots was larger than on typical conferences and offered plenty of time for discussions and to present the topic in detail. Furthermore, informal discussions took part during coffee and lunch breaks as well as during the social program.
Topics that have been discussed recurringly are:
fiber orientation analysis
As mentioned before, the orientation distribution of the short fibers causes anisotropic material behaviour. As a consequence, the fiber orientation needs to be assessed and monitored during, respectively after, the production of parts made of short fiber reinforced materials. Different methods to extract information about the positions and especially orientations by means of X-ray computed tomography have been discussed. Important aspects in these discussions have been the possibility to minimize user interaction and user mistakes, as well as the reliable separation of touching fibers to obtain information about individual fibers.
interface between fiber and matrix
Another important topic was the interface between the fibers and the matrix material, notably the interfacial transition zone (ITZ). The structure of the transition zone has great influence on the bond between fibers and matrix (stiction), and on the failure mechanism, like delamination of fiber and matrix, pull-out of fibers, friction during pull-out or rupture of the fiber in case of very strong bond/anchorage.
influence of fiber orientations on cracking behavior
The orientations of fibers have strong influence on the cracking and post-cracking behaviour of the composite material. After an initial micro-crack has formed, it could be bridged by fibers and these fibers could arrest the crack growth, in case of favourable fiber orientations. However, it is also possible, that fibers that are well aligned with each other, but have a “bad” orientation with respect to the acting forces can contribute to the formation of shear bands.
steel-, polymer and carbon-fibers at high temperatures; spalling
While the influence of short fibers on the tensile and compressive strenght of concrete has been investigated for some time already, the interest in high temperature properties and fire safety is a more recent development. It is interesting, that the addition of short polymer or carbon fibers has an influence on the fire resistance of, for example, concrete way above the melting temperature of the polymer fibers or even after the carbon fibers have been burned away in refractory composites. The polymer fibers help to avoid explosive spalling caused by high vapor pressure in the material as they influence the migration of the vapor. While in refractory composites the addition of fibers can have beneficial influence of the compressive strength even after the material has been heated to temperatures at which the fibers themselves have been burned out.
Many participants have expressed their wish to obtain the slides of other presentations and also to have full papers, this demonstrates both, the topical interest and the quality of the presentations. Also the wish to have future colloquia on this and related subjects has been expressed.
We thank Euromech for making the meeting possible and for the financial support.
Number of participants from each country
| Country | Participants |
|---|---|
| Germany | 5 |
| Estonia | 5 |
| Lithuania | 2 |
| Latvia | 2 |
| Spain | 2 |
| Finland | 1 |
| Sweden | 1 |
| Netherlands | 1 |
| Total | 19 |