Computational modelling of manually stitched soccer balls

Abstract

Soccer is the major ball sport, which attracts both viewers and participants worldwide. The primary equipment requirement is the ball, and the soccer ball market is as competitive as the game itself. The global interest of the sport provides an ideal international stage for the marketing of sports equipment such as soccer balls, boots, gloves, shin guards, and apparel. Multinational sports equipment manufacturers strive for superior product performance to enable commercial advantage, and the design and development of soccer balls is a crucial activity in achieving this. This work details the development of a finite-element (FE) model of a manually stitched textile-reinforced 32-panel ball used in an elite competition. A basic icosahedron FE model was produced to describe a thin-walled isotropic homogeneous shell, and this was subsequently enhanced to include a skeletal-like stiffer stitching region. Material testing was carried out to determine the mechanical properties of the bladder, outer panel, and stitching materials and prescribed within each model by a hyperelastic strain energy potential equation. A stiffness proportional damping coefficient was also used to describe kinetic energy loss characteristics. Each model was validated by an experimental impact testing under dynamic conditions that are representative of play, evaluation of coefficient of restitution, contact time, and deformation. It was found that the advanced soccer ball model accurately represented the deformation behaviour of the ball throughout impact.