Gert-Jan Kieft (Kiwa) | Photo: FOODNote
Kiwa ISA Sports tests sports materials and equipment for national and international sports federations. LABinsights took a tour of their recently completed lab facilities in Apeldoorn and saw how artificial turf, hockey sticks and tennis balls are tested.
Kiwa integrated the ISA Sports labs into its complex in Apeldoorn in the spring of 2023, moving about thirty employees to that location. The previous premises near Arnhem were not shuttered entirely, though.
Because of Kiwa ISA’s historical ties with the Dutch Olympic Committee and Dutch Sports Federation (NOC*NSF), the Olympic training center at Papendal, and some individual sports federations. The lab wanted to maintain a presence at Papendal and keep its office open there in any case.
Materials and Equipment
The lab facilities in Apeldoorn are accredited to test artificial turf, indoor sports flooring, and tennis courts, but also sports equipment such as tennis balls and hockey sticks. The clients who order these tests are equipment manufacturers, sports facility owners, and sports federations.
Some are Dutch organizations, others are international. The newly established laboratory uses standard lab equipment as well as custom, one-of-a-kind setups.
Kiwa HIC measurement | Photo: FOODnote
Accreditation
Kiwa ISA Sport and the laboratory have a reputation to uphold. In the Netherlands, they are accredited by major Dutch sports federations such as KNVB (football), KNLTB (tennis), KNHB (hockey), Atletiekunie (track and field), and KNKV (korfball).
At the international level, the lab has been accredited by FIBA, FIFA, World Rugby, ITF, FIH, and World Athletics. Only a few labs in the world can match these credentials.
Structures Lab
Just how unique Kiwa ISA Sport’s laboratory is becomes clear on our tour of the premises with Gert-Jan Kieft, lab manager at Kiwa Infra & Sport. The first stop is the structures lab, equipped to test the structures of layered floor systems.
This is where artificial turf, gymnasium floors and athletics tracks are tested. “We assess whether the substrates on which sports are played have the right technical characteristics such as damping, traction, and torsional strength.”
The tests take into account the standards that football or hockey cleats have to comply with and, for indoor sports, the norms that indoor shoes have to meet.
“We also test tennis balls’ bounce properties on tennis court surfaces to assess the speed of the court. Is it too fast, or too slow? We use a ball cannon to test the tennis balls’ bounce height. And we test the top layer, as well as all the other materials used in artificial turf systems.”
“We determine the bounce height based on the time between two bounces”
Gert-Jan Kieft, lab manager at Kiwa Infra & Sport
Measuring Bounce Height
The balls’ vertical bounce is precisely measured using a setup with a camera and a microphone, Kieft explains. “We determine the bounce height based on the time between two bounces. We primarily test with Adidas balls supplied by FIFA. We also certify hockey balls for the International Hockey Federation (FIH) and tennis balls for the International Tennis Federation (ITF).”
Kiwa also tests golf balls. “Our golf cannon shoots balls to test if their bounce height stays within the limits for natural grass.”
Playground Surfaces
Kiwa ISA Sport also tests whether playground surfaces are safe enough in case a child falls from a jungle gym.
“There are specific tests for playground surfaces to determine critical fall heights,” says Kieft. “This helps determine which surface is suitable under a particular type of playground equipment.”
The Head Injury Criterion (HIC) is a crucial parameter. Kiwa uses a heavy stainless steel ‘head’ to determine this. “This 4.5-kilogram metal shape has been equipped with sensors at several critical points. This allows us to measure the fall acceleration in all three axes, x, y, and z, which gives us an indirect deceleration. This will tell you the impact when hitting the ground.”
Testing the impact of spikes on a track and field surface | Photo: FOODnote
Artificial Turf Sliding Tester
A common issue for sports played on artificial turf is that sliding can cause burns. To mitigate this risk, sports organizations have set standards.
“We use the ‘artificial turf sliding tester for skin friction’ to determine the friction coefficient between a silicone skin and artificial turf, both dry and wet. This coefficient must fall within certain specified limits. Similar criteria apply to surfaces in gymnasiums and indoor athletics floors.”
Studded Roll Test
In the next room, we are shown various test setups, including one with studded rolls. The rolls rub back and forth on the artificial turf to test its durability. The results show the amount of wear and tear after five years of use. Granules are added to increase the wear.
“The rolls move back and forth 6,000 times. We evaluate the situation before and after. Then we test for torsional resistance and shock absorbency.” This accelerated aging test “puts more wear and tear on the turf in a week than athletes do in 5 years,” Kieft says.
Similar tests are conducted for tennis. “This studded roll test enables us to assess the durability of every type of tennis surface.” And it doesn’t stop there: “Even goal-line technology can be tested.”
Cutting artificial turf into squares for further testing, including a tensile test | Photo: FOODnote
Materials Lab Tests Plastic Fibers
As we move on to the materials lab, we see what looks a lot more like a typical laboratory. Testing equipment from familiar laboratory brands is used to determine pressure and tensile strength.
There are microscopes for studying the material in detail. “We examine the length and dimensions of the turf fibers, for instance. We put a cross-section of a fiber under the light microscope and compare it with a reference, or we count the density pattern of plastic fibers.”
“The trick in testing the tuft is to choose the right fiber in the bundle for a representative tensile test”
Gert-Jan Kieft, lab manager at Kiwa Infra & Sport
Elsewhere in the lab, an analyst is cutting artificial turf into pieces. “This is for testing tuft bind strength,” Kieft explains.
“Are the plastic fibers well bonded? If not, the top layer will quickly fall apart.” He points to the Zwick Roell Z 2.5 equipment used to carry out this test. “We call this the ‘Zwicky’. It has a highly sensitive sensor. The trick in testing the tuft is to choose the right fiber in the bundle for a representative test. That’s manual work that requires good vision.”
Studded roll equipment for measuring wear on artificial turf | Photo: FOODnote
Measuring Pressure and Tensile Strength
The impressive Zwick tensile and pressure benches subject the plastic blades of grass to enormous forces. “This is how we measure the tensile strength of the athletics mat. That tells you how much stretch it takes to break it and how elastic it is. We also use the pressure bench for repeated load tests. That’s how we establish whether walking on the artificial turf system or using heavy equipment for maintenance leaves any traces.”
The lab also tests the infill material in the turf system. “Rubber granules have memory; we compress them to 0.5 Megapascal for three days, followed by a day of relaxation. They should return to their original state.”
Tensile test on a tuft of artificial turf | Photo: FOODnote
Rubber and Fiber Fingerprinting
The lab also tests whether the materials used comply with the applicable material composition guidelines. ThermoGravimetric Analysis (TGA) is used to determine the nature of the components in rubbers and Differential Scanning Calorimetry (DSC) to see how much energy is required to determine the fiber melt point.
In both cases, the lab uses Perkin Elmer equipment and the resulting values are compared with a reference. The curves must exactly match those of the reference materials; if not, the composition has changed. “We create a fingerprint of the material, using TGA for rubbers and DSC for plastic fibers.”
“There are specific tests for playground surfaces to determine critical fall heights”
Gert-Jan Kieft, lab manager at Kiwa Infra & Sport
‘Torture Equipment’ for Sports Flooring
The lab conducts many more tests according to the FIFA test manual, such as drainage rate with and without infill. It also does a fire resistance test for artificial turf and an accelerated aging test with UV to determine the color differences of infills after prolonged exposure.
Another one of their tests measures the effect of 5,000 hours of ultraviolet radiation on the tensile strength of grass fibers because these should not become brittle.
The ‘Taber test’ and the ‘Spike tester’ are also notable. The Taber test is designed to measure wear and abrasion resistance of artificial turf. “This machine has a grinding stone to which the material is exposed 3000 times. We apply various fineness grades, depending on the standard. After the test, the material is allowed to show a maximum number of milligrams in wear.”
The Spike tester is a rotating rotor with spiked blades. Kieft describes this piece of ‘torture equipment’ for sports flooring as follows: “With the Spike tester, we can test the effect of spiked shoes on the surface and the substrate of the track. Using a cleat attachment, we can also use it to test the effect of cleats on the artificial turf. Or on rubber or cork, for that matter.”
