The mechanical behavior of twistless and twisted PET yarns used for tire cord construction has been investigated by means of monotonic and cyclic uniaxial tests conducted at room temperature. Under monotonically increasing strain, the force-strain curves exhibit a characteristic shape, with a change in concavity that appears at strain values below 2% and involves a stiffening behavior for higher strains. A new material model is here developed that includes, in addition to viscosity and plasticity, a nonlinear elastic behavior in the fiber direction aimed at capturing the stiffening behavior. This model is used in numerical simulation accounting for the local anisotropy, defined pointwise by the filament direction, which follows coaxial helices. The material parameters of the proposed constitutive model are identified using the experimental response of monotonic tests on twistless yarns and on a twisted yarn characterized by a specific construction. The model has been subsequently validated by simulating monotonic tests on twisted yarns of different constructions and cyclic tests on twistless and twisted yarns.
GentAWalterJ. The pneumatic tire, national highway traffic safety administration. US Department of Transportation, 2006.
2.
LeeHJKimSJYoukJH, et al. Properties and application potential of mechanically and chemically recycled pet fibers for tire cord and airbag applications. Fibers Polym2025; 26: 5393–5403. https://doi.org/10.1007/s12221-025-01183-w
3.
BehnkeRKaliskeM. Finite element-based analysis of reinforcing cords in rolling tires: influence of mechanical and thermal cord properties on tire response. Tire Sci Technol2018; 46: 294–327.
CaracinoPAgrestiSPires da CostaL, et al. The nonlinear behaviour of cords to be used in rayon-rubber composites. In: Constitutive Models for Rubber XII: Proceedings of ECMR2022, Milano, Italy (1st ed.). CRC Press, 2022. https://doi.org/10.1201/9781003310266-77.
6.
Pires da CostaLMoscatelliMCaracinoP, et al. Geometrical and mechanical modeling of polymeric multi-ply yarns. Appl Sci2024; 14: 14. https://doi.org/10.3390/app14114597
7.
TianLWangDSuP, et al. A study on the viscoelastic behaviors of tire cords using dynamic mechanical analysis. J Eng Fibers Fabrics2020; 15: 1–8. https://doi.org/10.1177/1558925020915195
8.
Hoo FattMSPakalaAKVedireAR. Properties of polyester tire cords for NVH applications: strain and frequency effects. J Appl Polym Sci2025; 142: 1–16. https://doi.org/10.1002/app.57762
ZimlikiDAKennedyJMHirtDE, et al. Determining mechanical properties of yarns and two-ply cords from single-filament data. Part II: comparing model and experimental results for pet. Textile Res J2000; 70: 1097–1105.
11.
SpencerAJM. Constitutive theory for strongly anisotropic solids. In: Continuum Theory of the Mechanics of Fibre-Reinforced Composites, Springer Vienna, 1984. pp.1–32. https://doi.org/10.1007/978-3-7091-4336-0-1
12.
KorunovićNFragassaCMarinkovićD, et al. Performance evaluation of cord material models applied to structural analysis of tires. Compos Struct2019; 224: 111006. https://doi.org/10.1016/j.compstruct.2019.111006
13.
ReeseS. Meso-macro modelling of fibre-reinforced rubber-like composites exhibiting large elastoplastic deformation. Int J Solids Struct2003; 40: 951–980.
14.
BedzraRReeseSSimonJW. Hierarchical multi-scale modelling of flax fibre/epoxy composite by means of general anisotropic viscoelastic-viscoplastic constitutive models: part I – micromechanical model. Int J Solids Struct2020; 202: 58–74. https://doi.org/10.1016/j.ijsolstr.2020.05.020
15.
BISFA-Standards. Testing methods for viscose, cupro, acetate, triacetate and lyocell filament yarns. BISFA, 2007.
16.
LechatCBunsellARDaviesP. Tensile and creep behaviour of polyethylene terephthalate and polyethylene naphthalate fibres. J Mater Sci2011; 46(2): 528–533. https://doi.org/10.1007/s10853-010-4999-x
17.
KrmelaJMichnaMRůžičkaZ, et al. Cyclic testing of polymer composites and textile cords for tires. Polymers2023; 15(10): 1–15. https://doi.org/10.3390/polym15102358
18.
ChoJRLeeHWJeongWB, et al. Finite element estimation of hysteretic loss and rolling resistance of 3-D patterned tire. Int J Mech Mater Des2013; 9: 355–366.
19.
O’SheaDJAttardMMKellermannDC. Anisotropic hyper elasticity using a fourth-order structural tensor approach. Int J Solids Struct2020; 198: 149–169. https://doi.org/10.1016/j.ijsolstr.2020.03.021
20.
BertCW. Models for fibrous composites with different properties in tension and compression. J Eng Mater Technol1977; 99(4): 344–349. https://doi.org/10.1115/1.3443550
21.
OgdenRW. Large deformation isotropic elasticity – on the correlation of theory and experiment for incompressible rubberlike solids. Proc R Soc Lond A Math Phys Sci1972; 326(1567): 565–584. https://doi.org/10.1098/rspa.1972.0026
22.
LemaitreJChabocheJL. Mechanics of solid materials. Cambridge University Press, 1990.
SibellasAAdrienJDurvilleD, et al. Experimental study of the fiber orientations in single and multi-ply continuous filament yarns. J Text Inst2020; 111: 646–659. https://doi.org/10.1080/00405000.2019.1659471
