Desso - Optimization of the Playing Properties of Artificial Grass Fields (2007 - 2010)

Desso Sports Systems and the Department of Textiles of Ghent University work together in this scientific research project involving a new type of artificial turf.

The most important aims of the project are:
• complete acceptance of artificial turf in the world of sports
• guaranteed quality as to playing properties (sliding, ball roll, ball bounce ...)

In order to meet these aims, the project involves:
• research into an optimal stalk of artificial turf based on fixed required characteristics
• research into and development of testing methods to translate intuitive aspects (e.g. sliding, ball contact,…) into objective criteria.

The use of artificial turf for sport surfaces has increased significantly in recent years. The reasons for this are various: climate and weather independence, better wear and tear behaviour compared to natural turf, less maintenance, a more even and uniform playing surface. Hence artificial turf is used in hockey fields for more than 30 years, and for many years it is commonly used in tennis and rugby. Recently, it is more and more used for football applications, especially with the development of the so-called “third generation” artificial turf, consisting of artificial fibres tufted on a backing with an infill of sand and rubber granules.

This “third generation” artificial turf – also called “football turf” – gets full support of official football organisations like FIFA and UEFA in their ambition to  standardise the football game. Despite this support, there is still quite some resistance among players and clubs. These prejudices are partly based on bad experiences in the past with older types of artificial turf, not adapted for the specific demands of football, but also on shortcomings of the newest types of artificial turf, specifically designed for football applications. One of the most frequently heard complaints is that the ball roll behaviour is different from the one on natural turf. In general, players tend to perceive that the ball speed is higher and it is sometimes considered too high.

It is known from experience that these ball roll problems on artificial turf start already a few months after installation. Whereas the ball roll behaviour on a newly installed artificial pitch is acceptable and even comparable to the one on natural turf, this is no longer the case for an artificial field that has been played on for some months. A clear degradation in playing quality over time is noticed. This is often indicated as a lack of “resilience” of the field.

If complete acceptance could be realized and artificial turf could substitute natural turf, a number of important advantages would appear:
• higher weather resistance, higher playability intensity ( > 2000 hours for artificial turf compared to ca. 300 hours for natural turf) and a higher multifunctionality.
• urban areas coping with a lack of space for sports facilities could offer a higher playability and hence accommodate more sports men.
• artificial turf is multifunctional i.e. the sports area can be more efficiently used.

To obtain a new development, research is done into new polymer mixtures and a new form of the ‘grass-stalk’ for sports applications. During this project, intense research is carried out to optimize the artificial turf fibres and structures. The resilience of the fibres will be studied more in detail and the polymer mixtures will be optimized to obtain better end-of-use properties over a longer time period.

The water absorption of the fibres is an important parameter for the temperature control of the artificial turf field, for the friction and interaction with the human skin. Fibres with a higher capacity of water absorption will be studied and developed in this research project.

The development of an alternative turf will be done according to existing and newly determined criteria and numerical simulations. The choice of the materials and the construction of the turf will be emphasized. The aim is to integrate more sports-technical properties. Currently, no objective criteria exist which translate the subjective experience of the playing behaviour on a turf. Hence there is a need to develop measuring methods to validly and objectively determine subjective
observations (e.g. sliding). To this end, the most recent knowledge of polymer and fibre technology will be appealed to, supported by an extensive set of testing and measuring devices for both laboratory and field tests. For these reasons, the laboratory is working on new testing methods: sliding tester, filament resilience, 12m-lisport, ... An important testing method for artificial turf resilience is the 12m-lisport. The lisport wearing machine is the most frequently used apparatus for artificial turf. Vertical ball rebound, rotational resistance, shock absorption, energy restitution and vertical deformation are determined. All of these parameters are determined by the infill and underlayers rather than by the type of yarn. The most important parameter for testing the yarn quality is the ball roll. For that reason, the Department of Textiles has built the 12m-lisport machine.

Another property of artificial turf is the prevention of burns when a sliding is being performed. Since the existing standardisation is insufficiently developed in this respect a new testing method was developed.

In the existing standards, there is no mention of a temperature change measurement during the sliding, although this appears extremely relevant in the light of the possible occurrence of burns. The developed test set-up approaches the sliding phenomenon in a more realistic way, having the following advantages: a linear movement over a realistic sliding distance (instead of a rotating movement on a small piece of grass), a decelerated movement, a realistic order of magnitude of load and a temperature measurement. A good and reliable experimental method was developed for the measurement of the temperature increase at the surface of the skin during a sliding. A theoretical approach of the sliding was studied and the results correspond very well to the practical results. A simulation of the temperature increase during a sliding is possible and the influence of different parameters can be studied directly from the calculations, together with their importance on the temperature increase during the sliding. This temperature profile during a sliding can be very important for the comfort of the player in combination with other characteristics of the field as shock absorption, energy restitution, quality of the yarns…

This project wants to contribute to a breakthrough in the acceptance of artificial turf for football, having constant playing properties during the whole season.


Research is being done in co-operation with the Department of Material Science & Engineering and the Department of Movement and Sports Sciences of Ghent University.

Contact:

Prof. dr. Dagmar D'Hooge (dagmar.dhooge@UGent.be)
Lic. Stijn Rambour (Stijn.Rambour@UGent.be)