Artificial Turf Gains Ground with Realistic Simulation

• Analytics & Modeling - Digital Twin / Simulation

• Product Research & Development

• Digital Twin
• Virtual Prototyping & Product Testing

• Software Design & Engineering Services

The Fédération Internationale de Football Association (FIFA) has set detailed regulations about the materials, substructure, installation, testing, and certification of artificial turf for playing fields. This means that turf manufacturers have to consider a multitude of factors when designing their products for performance and safety. These factors include the make-up of the individual blades to mimic the look and playing-feel of natural grass, the type of yarn/fiber to use, the shape of the fiber, its height above the field surface, its density per square meter, stiffness and dissipative behavior. All these factors affect wear, safety, and playing characteristics. Furthermore, what’s below the visible surface of the grass is just as critical. The fiber travels down through infill made of rubber or thermoplastic granulate, which provides shock absorption, controls rebound and prevents skin damage caused by sliding. Beneath that are additional layers of rubber and sand and, finally, the backing in which the grass blade is imbedded.

Royal TenCate is the world’s leading producer of synthetic grass fibers and other components for playing fields. The company caters to various sports including soccer, American football, rugby, field hockey, or lacrosse. A playing field must be able to take a significant amount of pounding from feet, sports balls, and falling bodies. Add different climates (hot versus cold, wet versus dry) and impact patterns (heavily padded American football teams versus bare-kneed soccer players) and you begin to get an idea of the design variables that TenCate must take into account when designing artificial turf. The company makes distinct types of polyethylene grass fibers, plus thermoplastic infill material, and polypropylene woven backing fabrics—all of which must work together for optimum results.

To meet the stringent requirements set by FIFA, TenCate turned to Abaqus finite element analysis (FEA) to model their turf design. The software was chosen due to the breadth of its materials models and its ability to model the individual characteristics of each component and relate that to the behavior of the total system. When creating artificial turf models, TenCate looks at the problem at a number of levels: micro, the properties of an individual fiber; meso, grains of infill interacting with fibers; and macro, a ball or player impacting the field. A grass-fiber model in Abaqus can be subjected to virtual bending tests, and its mass, shape, height, etc. modified and retested, until the desired characteristics are achieved. Infill models can be adjusted for morphology, size, material, distribution, friction and layer thickness, and then run through triaxial (three-dimensional) compression tests. An entire square of turf, with fibers, infill and backing characteristics built into the model, can be evaluated for compression by a virtual foot or a bouncing ball.

• By using FEA during product development, TenCate can simulate the effects of the artificial athlete tests on their turf models. This allows them to evaluate the performance of different combinations of turf fiber, infill and backing, and make modifications that will optimize the turf’s performance in the outdoor tests.
• A ball-bounce analysis is set up using an FEA shell model of a ball full of gas at the correct pressure. For comparison, a real ball is bounced off a surface and the rebound results are then factored into the simulation of the synthetic turf response and used to make product modifications as needed.