Tyres are largely composed of cord-rubber composites, which are subjected to varying operating conditions.  Probability of failure in tyres is generally high at the belt edge and ply turn-up edge interfaces where stiffness discontinuities exists.  Several studies are being conducted using Finite Element (FE) techniques to study the design and performance of tyres.  In these FE studies, orthotropic properties of the cord rubber composites are generally defined by REBAR technique (Abaqus FEA solver), which assigns equivalent stiffness properties to the host rubber. However, this methodology does not capture the crucial interfacial stresses between the individual reinforcements and the rubber matrix. Hence, these regions need to be studied in detail in order to predict probable failure zones and for design optimization.

In the present work, a global tyre model was subjected to regular operating conditions using the standard FE technique.  The belt edge interface region was chosen for a subsequent local FEA. A detailed 3-D micromechanical model consisting of individual twisted ply cords embedded in rubber, with the double curved structure was modeled.  A global-local FE analysis of the sub-model was performed. The resulting stress distributions were studied.

Optimization of various design attributes such as the spacing between the individual cords, the twist geometry is performed for the interface stresses between the cord and the rubber matrix.  An attempt has been made to study the origin and initiation of the crack in the possible failure zones using cohesive elements.  A detailed procedure to optimize the cord-rubber characteristics is thus established which forms an useful tool to tyre designers.