A study of creep in polycarbonate fused deposition modelling parts

This paper presents an experimental investigation on the influence of process parameters such as part orientation, air gap and number of contours along with their interactions on the creep behaviour of fused deposition modelling (FDM) processed polycarbonate (PC) parts. Due to the lack of creep curve data with parts processed by FDM, this research gives a first quantitative approach to the time-dependent mechanical properties. This study not only varies significant process parameters viz., part build orientation, raster to raster air gap and number of contours, but also applies different loads to the samples to further understand primary and secondary creep behaviour for PC, providing the creep curves. Furthermore, two mathematical models are used to fit the experimental data, which can be used in numerical modelling. The first model is the well-documented and commonly used Bailey-Norton equation. As a second model, the fractional Voigt Maxwell in series (FVMS) is proposed to use. This model applies fractional calculus to reduce the number of parameters to be calculated. Conclusions obtained about how process parameters affect the creep behaviour are in agreement with previous research in mechanical properties of FDM parts.