An experimental and numerical investigation of deformation and fracture of semicrystalline polymers under varying strain rates and triaxial states of stress

摘要

The results of quasi-static tensile tests on POM and UHMWPE show that both materials are sensitive to strain rate changes and that the ductility of notched specimens is strongly dependent on the notch profile radius i.e. on the initial triaxial state of stress at the centre of the specimen. For POM, as for most ductile metals, a clear negative exponential relationship is demonstrated between local strain and σ_m/σ_e at fracture which would enable a relatively simple numerical failure model to be generated. In contrast, the much greater deformation and molecular orientation of the UHMWPE specimens cause significant changes to the stress triaxiality and strain rate during the course of the test. No simple relationship between strain and σ_m /σ_e at fracture can therefore be established and a more complex failure model that allows for path dependent damage accumulation is required.