Material extrusion additive manufacturing of Acrylonitrile-Butadiene-Styrene: Experiments and anisotropic model for the orientation angle

Abstract

The yield stress as a function of both strain rate and orientation angle was measured for material extrusion additively manufactured (ME-AM) Acrylonitrile-Butadiene-Styrene (ABS). Unidirectional test specimens were extracted by waterjet-cutting at different orientation angles from ME-AM processed plates. By printing rectangular plates, a strand trajectory of constant length can be applied. Thus, the thermo-mechanical history of the material was as similar as possible across the plate. By determining an average sample porosity using Archimedes’ principle, yield stress values could be compensated for the voids present in ME-AM specimen. A time- and orientation-dependent model, which combines an Eyring flow rule with Hill anisotropy, was used to describe the yield stresses as a function of strain rate and orientation angle. The model uses a factorizable approach, i.e. both effects are decoupled, which simplifies the determination of model parameters. This anisotropic continuum-based viscoelastic Eyring-Hill model is able to adequately predict the complex experimental yield stress behavior, which is a challenging task. Scanning Electron Microscope fractography revealed macroscopically more ductile behavior due to failure in the strand direction. Macroscopically brittle behavior was related to inter-strand failure. The present study is an important step towards the prediction of structural integrity of ME-AM parts, as time- and orientation-dependency are also important in creep and fatigue behavior.