Evaluation of deformation-induced anisotropy for plastically deformed polycarbonate

Abstract

In the present study, the deformation-induced anisotropic mechanical characteristics and the strain distribution are evaluated from the specimens cut from the necking part of polycarbonate. First, large specimens are used to create deformation-induced anisotropy in the necking part via a uniaxial tensile test. Next, the small specimens are cut from the necking parts in an arbitrary direction with respect to the tensile direction of the large specimens. The anisotropic mechanical characteristics in the small specimens are evaluated by a uniaxial tensile test and the strain distribution is measured by the digital image correlation. The result shows that the stress-strain curve of the small specimen depends on the cutting angle to the tensile direction of the large specimens. The elastic modulus and the maximum stress of the small specimens are maximum in the tensile direction of the large specimen, and the elastic modulus and the maximum stress decreases with increasing the cutting angle. Therefore, the deformation-induced anisotropic mechanical characteristics in the necking part are observed. In addition, if the uniaxial tensile direction to the small specimen differs from that to the large specimen, a shear strain band appears in the small specimen and the longitudinal direction of the shear strain band is affected to the tensile direction of the large specimen. The test results indicate that the anisotropic elastic modulus and the anisotropic characteristics in the plastic region are expressed by the anisotropic elastic constitutive equation and the Tsai-Hill criterion, respectively. Moreover, the anisotropic strain hardening is revealed because the Tsai-Hill parameters depends on the plastic strain.

Keywords

• thermoplastic
• necking
• deformation-induced anisotropy
• elasto-plasticity
• digital image correlation