Polyamide 6 (PA6) is a semi-crystalline thermoplastic used in many engineering applications due to high strength, good chemical resistance, and excellent wear/abrasion resistance. A thorough understanding of molecular structure – mechanical property relationships is necessary to design improved PA6 composite materials. The mechanical properties of PA6 are dependent on two forms of crystallinity (alpha/gamma) as well as strain rate. Semi-crystalline thermoplastics have a hierarchical microstructure spanning length scales, necessitating the use of a multiscale model.<br/>The multiscale model, comprising molecular dynamics (MD) and NASA Glenn Research Center’s micromechanics software MAC/GMC, was used to predict elastic moduli of semi-crystalline PA6 as a function of crystallinity and strain rate. The recently developed reactive INTERFACE force field (IFF-R) was used to predict elastic moduli of amorphous PA6 as a function of strain rate. The inputs to the multiscale model were the elastic moduli of amorphous PA6 as a function of strain rate as determined via MD and the stiffness matrices of the alpha and gamma crystal forms of PA6 as calculated by Tashiro and Tadokoro. The amorphous MD results show a strong strain rate dependence of the elastic moduli, thus validating IFF-R’s use in predicting the strain rate effect. The semi-crystalline multiscale model results show an increase in elastic and shear modulus as the strain rate and crystallinity increases.

Predicting the effect of crystallinity and strain rate on elastic moduli of PA6 using multiscale modeling

ACS Spring Meeting 2021

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