Uniaxial and biaxial experimental investigation of glassy polymers

Abstract

The alignment of polymer chains within polycarbonate (PC) significantly influences the mechanical properties of the deformed specimen. This influence can be affected by both the global stretch rate and the type of loading. The objectives of the current work are to investigate uniaxial film, bar specimens, and biaxial thick-walled specimens using 3D-optical measurements.Our approach involves developing different methods to determine the local inhomogeneous strain fields for both thin and thick-walled uniaxial specimens. In the pure tension case and under the assumption of uniaxial plane stress, we utilize the strains to calculate the local volume ratio and, consequently, approximate the local true stress at different axial positions of the specimen. Additionally, we investigate the effect of variations in global stretch rates on local stresses. Furthermore, we explore induced anisotropy for different global stretching ratios.Another objective is to investigate biaxial specimens under sequential and simultaneous biaxial stretching conditions, examining the impact of both stretching types on the mechanical and structural properties of the material.