[SY-H4] Symposium H-4

[SY-H4] Thermo-mechanically coupled model for large strain of ultra-high molecular weight semi-crystalline polymers

^○Chrystelle A. Bernard¹, Tiana Deplancke⁴, Olivier Lame⁴, Kazuhiro Ogawa³, Jean-Yves Cavaillé² (1.Frontier Research Institute for Interdisciplinary Sciences (FRIS), Tohoku Univ., Japan, 2.Engineering Science Lyon Tohoku joint lab for Materials under Extreme Conditions (ELyTMaX) UMI3757, Tohoku Univ., Japan, 3.Fracture and Reliability Research Institute (FRI), Tohoku Univ., Japan, 4.Materials Engineering and Science (MATEIS), CNRS, INSA-Lyon, UMR5510 Univ. de Lyon, France)

Polymers are largely used in everyday life; however, their large strain behavior is still not well understood because of the complexity of the mechanisms involved in their deformation. To improve the current knowledge on these materials, extensive experimental and theoretical researches have been performed leading to development of constitutive numerical models to predict their large strain behavior. Most of models based on polymer physics have been developed for amorphous polymers. The few ones predicting the mechanical behavior of semi-crystalline polymers do not consider the important evolution of microstructure occurring during the plasticity. This is especially true for ultra-high molecular weight semi-crystalline (UHMWSC) polymers. Because their microstructure exhibits very long macromolecular chains, one chain belongs at the same time at the crystal network and macromolecular network. During the plastic deformation of the polymers, fibrillation process occurs leading to the progressive collapse of the crystalline network and inducing strong variations in the material mechanical properties. Thus, to accurately predict the mechanical behavior of UHMWSC polymers, the mechanical coupling between crystallites and fibrils and its evolution during the deformation has to be taken into account. From the expression of the mechanical coupling for the elastic modulus given by Humbert et al. [1] (non-parallel/non-series configuration), Deplancke et al. [2] developed a one-dimensional model for the prediction of the mechanical behavior of Ultra High Molecular Weight PolyEthylene (UHMWPE). However, to extend its possible range of applications, transformation into a three-dimensional model is needed. Therefore, we have developed a 3D model which take into account the evolutive mechanical coupling, between crystals and fibrils, as a function of the deformation. The model is based on series configuration with consideration of the crystal ratio in the definition of the deformation gradients. Good agreement is found between the experimental results and 3D numerical predictions during loading and unloading.

[1] Humbert et al., Polymer 52 (2011) 4899-4909

[2] Deplancke et al., on going