FDM 3D-PRINTED THERMOPLASTIC ELASTOMERS: EXPERIMENTS, MODELING, AND INFLUENCE OF PROCESS PARAMETERS ON PROPERTIES

Soft, ultra-stretchable thermoplastic elastomers have recently became available for use with desktop, fused deposition modeling printers. However, the effects of additive manufacturing process parameters on final mechanical properties are presently not well-known for this class of materials, making predictive modeling and product design difficult. Here we perform a design of experiments investigation of an elastomeric material that the manufacturer claims to have up to 580% strain at fracture. Within the investigation, two factors, extrusion temperature and layer height, are selected as independent variables and mechanical properties are extracted as dependent variables based on quasi-static tension tests following ASTM D412. Primary statistical results, based on an Analysis of Variance, indicate that hotter extrusion temperatures exhibit higher Young's moduli (at small strain), lower ultimate tensile strength, and higher fracture strain. Further, the layer thickness is not a factor unless evaluating performance at small strain, in which case it is significant and thicker layers will yield higher Young's moduli. Several popular hyperelastic constitutive models are calibrated to our tensile data, and a preliminary finite-element simulation of a soft prosthetic finger is performed to demonstrate the potential role of predictive simulations in 3D-printed product design.