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Polyethylene terephthalate (PET) textile multi-ply yarns, or cords, are widely employed in the automotive industry as reinforcement in rubber-based tyres to carry a significant part of the loads and maintain the overall shape [1]. They are typically obtained by twisting together multiple yarns, i.e., twisted bundles of flat filaments with a certain number of twists per meter.
In [2], a three-dimensional elastic-viscoplastic model for rayon cords, which couples the anisotropic behaviour of the single flat filament with its complex geometric orientation induced by the twisting, has been proposed and used to simulate monotonic and cyclic uniaxial tensile tests.
In this work, we present the results of the experimental campaign conducted in Pirelli Tyre laboratories according to ASTM standards, to characterize the mechanical behaviour of PET cords in confined compression and bending. Specifically, compression tests are performed on a cylindrical rubber specimen with an embedded cord, while the three-point bending tests are performed on strips of fabric made up of 10 warp PET cords with a thin weft of cotton yarns. Then, the model proposed in [2] is adapted to PET and employed to simulate the compression and three-point-bending tests. This allows the identification of material parameters in compression and assess the capability of the model to predict the mechanical response of PET cords.
[1] B. Rodgers, Tire Engineering: An introduction, CRC Press, 2020
[2] L. P. da Costa et al., Geometrical and Mechanical Modeling of Polymeric Multi-Ply Yarns. Applied sciences 14, 2024