An Experimental Investigation of Polymer Additive Manufacturing

The objective of this research is to examine the design, qualification, and performance of additive manufactured (AM) parts made using ABS-P430 polymer material. A group of tensile and fatigue coupons were designed and manufactured using two fused deposition additive manufacturing machines, Stratasys SST 1200es and Creality CR-10. The AM parts were built on flat and on edge side at different build orientations. The influence of the manufacturing parameters on the mechanical properties of AM components were investigated. This includes the variation in building orientations, layer thickness and the distribution of air gaps. Tensile tests were performed to ascertain the tensile properties of the AM polymer parts. Full field strain measurements were obtained using 2D digital image correlation (2D-DIC). ANOVA statistical results showed that building orientations influenced the ultimate tensile strength and Young's modulus. There are slightly difference in the tensile properties with the variation in building orientation that is probably not statistically significant. The uncertainty propagation in tensile properties associated with the measuring instruments was calculated using the Guide of Uncertainty Measurement (GUM). The effect of build orientation on constant amplitude fatigue performance at initiation, propagation and overall fatigue life was investigated. The 2D-DIC method was successfully used to non-invasively measure the fatigue crack length. Fatigue cracks were measured during tests with frequent pauses, less frequent pauses and no pauses to identify the possible influence of test method on measured fatigue life. It was determined that the stress relaxation happening during the pauses had significant impact on measured fatigue life. The optical analysis was conducted to examine the link between process parameters and part defects. The fracture surface morphology analysis revealed that the void formation between deposited filaments affected the fracture surface. The void fraction percentage was estimated using optical methods. Specimens with more voids as measured by SEM had lower mechanical properties. Micro-CT analysis was selected to investigate the internal geometry of AM parts made from ABS polymer material. Also, Micro-CT was used to study the effect of contour width to total width ratio and contour area to total area ratio on the fatigue life of AM parts.