Investigating the mechanisms of traction on artificial turf surfaces

<p dir="ltr">Traction is a key factor influencing both performance and injury risk in sports played on third-generation artificial turf surfaces. Despite extensive research on boot design, surface characteristics, and loading conditions, the underlying mechanisms responsible for generating traction forces remain poorly understood. Previous studies have hypothesized these mechanisms, yet experimental evidence remains limited.</p><p dir="ltr">Styrene-butadiene rubber (SBR) is currently the most common performance infill material used in surfaces; however, the use of sustainable infill materials is increasing. As sustainable performance infill materials such as cork and pine become more common, artificial turf surfaces may exhibit a wider range of performance characteristics due to differences in mechanical properties of the surface. Therefore, understanding the interactions at the boot-surface interface during traction generation is more critical than ever.</p><p dir="ltr">This research aimed to develop a new conceptual model for traction mechanisms, supported by experimental evidence of the interactions occurring at the boot-surface interface. A secondary objective was to examine the relationship between different performance infill materials and the traction generated during testing.</p><p dir="ltr">To achieve these aims, an automated rotational traction tester (ARTT) was designed, manufactured, and validated to enhance the research capabilities at Loughborough University. The ARTT incorporated improved loading capacity, greater control and repeatability during rotations, interchangeable test feet, and an optical measurement technology to investigate traction mechanisms in greater detail. The integration of optical measurement technology enabled quantitative analysis of the interactions at the boot-surface interface for the first time in the literature.</p><p dir="ltr">Findings from this research were incorporated into a new conceptual model of traction. Optical measurement studies revealed a bulk movement of performance infill material during the initial stages of rotation and increased infill displacement on the path of the studs at larger displacements. The performance infill material within the surface system influenced both traction generation and its relationship with key variables such as normal load and rotational velocity. The effect of stud penetration on traction generation was included in the model, while the previously hypothesised dynamic friction force between the surface and test foot was removed. </p><p dir="ltr">This new evidence-based conceptual model of traction enhances understanding of traction mechanisms and can inform future research projects to support developments in surface and boot design, as well as governing body standards for artificial turf testing. By integrating the findings from the research project into future studies, surfaces and test methodologies, the safety and performance of sports played on artificial turf surfaces can be maintained and potentially improved.</p><p dir="ltr">This research is presented in an alternative thesis format, incorporating published journal articles in place of standard chapters. This approach ensured the publication of findings to the scientific community and industry stakeholders while maintaining the rigour of peer-reviewed research. By structuring the thesis around published work, each study presented is a standalone contribution to knowledge while also forming a cohesive narrative that advances the understanding of traction mechanisms on artificial turf.</p>