Strain gradient plasticity for amorphous and crystalline polymers with application to micro- and nano-scale deformation analysis

Microscale mechanical responses of semicrystalline glassy polymers are of utmost importance when these materials are deployed in microstructural applications, e.g. MEMS and NEMS. The classical continuum plasticity theories become ill-posed in the case of highly localized deformations and they result in mesh dependent Finite Element (FE) solutions. Then the continuum theories may not directly be applicable to study stress–strain responses in nano- and micro-scale structures. The non-local modeling approach is one solution to this deficiency in which the non-local effects, associated with the presence of highly localized plastic deformation fields, are integrated into the constitutive relations. The microstructural information together with the intrinsic material length scale are incorporated in these theories to take into account the non-local effects and to ensure the well-posedness of the governing equations. While non-local theories have been extensively investigated for Metals (class M materials), this work aims to develop a rate dependent plasticity theory with strain gradient effects for semicrystalline Polymers (class P materials).