D. Boisnard Labosport

I INTRODUCTION :

The presentation of the apparatus LISPORT, which is a device to assess the resistance to studds of synthetic turfs, was based on a video demonstration. For a better understanding, the photo of the apparatus is done fig 1 :

For many years, synthetic turfs have been classified, in France, in the unbound mineral surface area.

The main assessment referring to the standard was resistance to studds (with a repeated impact machine) in term of resistance to abrasion, with the calculation of weight loss or heigth loss.

Nevertheless, « bad surfaces » can lose little height but can compact a lot. So the resistance is good but the lost of the performance characteristics is bad.

After viewing the Balsam Lineartest based on the Lisson test (in textiles) and with the financial support of the «Mairie de PARIS », we built a first apparatus more simple and with the ability to test a larger sample.

The aim was not only to know what the durability of the fiber (fibrillation, breaks….) is but to check the modification of sport performance characteristics and safety characteristics.

It means :

• Shock absorption
• Energy restitution
• Deformation
• Ball bounce
• Water infiltration

In the mean time we have assessed 18 turfs in Paris since 1993, every two years, and more than 150 pitches are now tested in France.

II ASSESSMENT : accelerometric method :

The assessment of turfs and samples is based on the French standard NF P 90 104 : accelerometric test. An impactor of 8 kg hits the surface with a free falling height of 7, 10, 13 cm.

(in the tables we will report only the average falling height of 10 cm).

The calculation determines :

• Deceleration of the impactor in g (shock absorption)
• Final speed of the impactor in m/s (energy restitution)
• Maximum deformation in mm (suppleness)

For ball bounce, the tests were carried out according to the European draft.

The first information after the test were :

• Importance of shock pad for the shock absorption result 
• Importance of the shock pad for the energy restitution 
• Both influence of shock pad and turf for the deformation, but more importance of the turf regarding the ability of no compaction
• No real correlation between energy restitution and ball bounce (too different energy), ball bounce depends on the turf quality and the ability of no compaction 
• Large influence of the sand on the compaction (means less deformation).

III SYNTHETIC TURF REQUIREMENTS :

With the advisement of the French Federation of Football, around 20 natural pitches were tested with the same accelerometric method and requirements were proposed and adopted in France for synthetic turfs.

In table 2, we present these requirements :

• MAXIMUM DECELERATION = SHOCK ABSORPTION
• FINAL SPEED = ENERGY RESTITUTION
• DEFORMATION = SUPPLENESS

For information we present different ranges of results (table 3) :

Natural turf means high quality level of turf with 3 cm turf height (average)

Values from pitches : in the same time we assessed many synthetic turf pitches and the range of results was wide. Many pitches were hard and out of the standard.

COMPARATIVE RESULTS :

N.B. : Falling height = 10 cm (medium energy)

IV DESCRIPTION OF THE APPARATUS LISPORT :

The apparatus includes 3 movements : a linear movement of the two studded wheels, a transversal movement of the supporting sample plate and a sliding movement of one wheel (20 %).

Main characteristics :

• Weight of each cylinder : 27 Kg
• Number of studds for each cylinder : 96
• Dimension of cylinders : 11,8 cm by 30 cm
• Length of the chassis : 80 cm
• One cycle of movement : 6.50 seconds
• One cycle of transversal movement : 2.30 seconds (1.9 cm)
• Dimension of the samples : 80 by 42 cm

V EXAMPLES OF REPORT :

(in this summary we present only one assessment).

USURE AUX CRAMPONS - LISPORT

Nombre de cycles  : 2000 n° Produit : 990190 R
Date  : 21/04/1999
Dénomination :
Descriptif :

Le revêtement destiné aux terrains de grands jeux en utilisation football, est un gazon synthétique non sablé en fibres frisées, monofil, de 14 mm de hauteur, de couleur verte, tufté en chevrons, à base de copolymère.

Complément (aspect fibre) : fibres couchées (perte de hauteur : 4 mm)

LONGUEUR TOTALE DU FIL :

Avant  : 30 mm
Après : 30 mm
Perte : 0 %

ACCELEROMETRIE  : (hauteur de chute : 10 cm) selon la norme NF P 90 104

Sous-couche utilisée : REGUPOL 5410 – 4,8 – 10 mm
Sable utilisé : /
Hauteur du sablage : / mm

CONCLUSION : B. B. : 66 % 80 %

Après usure aux crampons LISPORT, le produit est CONFORME à la Charte Qualité Garantie Construction (FNCESEL), et aux exigences FFF (01/99).

(Ce rapport n’est valable que pour un complexe incluant les mêmes matériaux).

VI COMPARISON TEST/SITE : EXAMPLES

1 : Coignières  Max/alv:

2 : Sannois  Max/enk:

(Goal 1994  = 8.3)

3 : Biancotto int/reg :

4 : St Martin opt/rbs :

(goal 1999 : 7,1)

5 : Paul Valery opt PE/reg :

6 : La Plaine 3313/pol :

7 : Elisabeth Twi/enk

In 1994 , the turf was removed in the testing area (not the shock pad) and a program of maintenance was done.

VII CONCLUSION :

The conclusions of the research which is still in progress are :

• The correlation with the practice is good. We assess all the different changes in the turf quality : fibrillation, too high abrasion, breaks.
  
• This correlation is between 4 and 6 years with 2000 cycles (one day). This correlation will be adjusted.
  
• The apparatus is useful for manufacturers and applicators to be certain to fill the requirements of the standard during the guarantee period of 5 years ( general quality plan in France). The French Federation of Football homologates the syhthetic turfs every 5 years.
  
• The apparatus is useful for the laboratories to assess the durability of sport performance characteristics of the sport surface : shock pad + turf + sand.
  
• The apparatus could be useful for research and for other fields : resistance to spikes of synthetic surfaces for tracks, resistance to abrasion for indoor surfaces and tennis surfaces. Many devices could be added.