Mechanistic study of cord angle influence on air spring torsional and roll stiffness and its effects on suspension cornering performance

Abstract

Air springs play a pivotal role in modern vehicle suspensions by influencing roll stability, ride comfort, and lateral load transfer. Although extensive research has focussed on their vertical stiffness, the torsional characteristics—crucial for cornering dynamics—remain inadequately understood. This study introduces a novel coupled modelling and simulation framework that bridges the material-scale mechanics of reinforced rubber with full-vehicle dynamic responses. A high-fidelity finite element (FE) model of a diaphragm-type air spring is developed, integrating nonlinear hyper elasticity, cord anisotropy, and gas–structure coupling to capture torsional stiffness variations under combined loads. A new analytical torsional stiffness formulation is derived, explicitly linking cord angle to the air spring’s macroscopic stiffness and revealing nonlinear dependencies neglected in previous models. Furthermore, a three-degree-of-freedom (3-DOF) suspension model is implemented in Simulink to quantify the effects of torsional–roll coupling on roll angle and yaw rate during cornering manoeuvres. The results show that decreasing the cord angle from 64° to 44° increases torsional stiffness by 20%–35%, enhancing roll stiffness proportionally and reducing the roll angle and yaw rate by up to 21.9% and 19.7%, respectively. The proposed framework provides a theoretical and computational foundation for optimising air spring geometry and improving vehicle handling, stability, and ride performance.