Investigation of stereolithography material by depth sensing indentation and differential scanning calorimetry

Abstract

Depth sensing indentation (DSI) has been used to investigate the mechanical properties of the epoxy based resin SL7580, which was manufactured by the stereolithography (SL) process. Post-processing techniques used in the SL process have been studied and their influence on mechanical properties determined. Depth sensing indentation has been used to investigate differences in the polymerisation process in the border scan (edge) and the hatch scan (centre) areas. These experiments showed a higher scatter in the indentation hardness at the edge of the sample than in the centre. This was attributed to the higher surface roughness at the edges, as measured using atomic force microscopy (AFM). Changes in mechanical properties with respect to time were also observed and these were attributed to post-curing of the SL7580. The curing kinetics was investigated using differential scanning calorimetry (DSC) and found to fit a simple mechanistic model. The predicted degree of cure was found to correlate well with the measured indentation hardness and modulus and a simple method of predicting the variation in mechanical properties with time is proposed.