Abstract
Yield in a semi-crystalline polymer involves the disruption of the crystalline phase in an irreversible deformation process. In a semi-crystalline polymer, the crystalline lamellar regions are bridged together by inter-lamellar amorphous layers, which act as a loading transfer medium. The deformation of both phases is, therefore, to some extent inter-related. In this work we adopted a continuous mechanic approach (neglecting atomic/molecular interactions) of the lamellar deformation of semi-crystalline polymers in the sense that we simulated the mechanical response of a lamellar structure (two lamellae interconnected by amorphous regions) in a finite element analysis. The use of computer simulations allows studying independently the effect of each relevant morphological parameter on the mechanical response. Several simulations were performed considering isolated variations of the following morphological parameters: i) mechanical behaviour of the amorphous material; ii) thickness of the crystalline regions; iii) length of the amorphous regions; iv) number of amorphous regions connected with a crystalline lamella; v) relative angle between the crystalline and the amorphous regions; vi) mode of loading (tension and compression). The thickness of the crystalline lamellae is evidenced as the most significant factor affecting the tensile response of the lamellar structure, followed by the mechanical behaviour of the amorphous phase. The connection angle between amorphous and crystalline regions and the number of amorphous regions bridging adjacent crystalline lamellae play only a minor role. The length of the amorphous regions has a negligible influence. As expected, the lamellar structure shows also distinct behaviours under distinct loading modes, tensile loading showing the highest stresses.
© 2013 by Walter de Gruyter GmbH & Co.
