Study on the static and dynamic mechanical properties and constitutive models of 3D printed PLA and PLA-Cu materials

Abstract

The failure of mechanical properties in 3D printed polylactic acid (PLA) for many functional applications has made exploring ways for improving these properties essential; the use of copper powder for producing a composite material known as PLA-Cu is one of these ways. The mechanical responses of both PLA and PLA-Cu under both static and dynamic loading were studied using a universal testing machine and a split Hopkinson pressure bar apparatus, respectively. This experimental study helped to develop a constitutive model for each material according to their mechanical behavior. However, PLA-Cu, affected by ‘impact embrittlement,’ indicates a purely linear elastic behavior during dynamic conditions. Addition of copper powder increases the yield strength of the composite material significantly as compared to pure PLA, with both materials being strain rate sensitive as they change from static to dynamic states. The calibration of the Johnson-Cook constitutive model with the inclusion of the Cowper-Symonds strain rate term for these materials promises useful information for numerical models, improving the predictive models on their behavior under different loading scenarios.