Morphology and Weld Strength of a Semi-Crystalline Polymer Produced via Material Extrusion-Based Additive Manufacturing

Material extrusion-based additive manufacturing, also known as fused filament fabrication, is a big research topic nowadays. In this process, a thermoplastic filament is melted and deposited onto a build platform according to a predefined path. That way a component is created layer by layer. However, thereby numerous weld lines are formed which mostly represent the weak spots of additively manufactured components.
This study aims at analyzing the strength of such weld lines for a semi-crystalline polymer. Therefore, one strand thick boxes were printed at different processing conditions. During the manufacturing of the boxes, the temperature of the deposited strand was recorded by means of an infrared camera. Afterwards, tensile test specimens were prepared from the boxes and tensile tests were carried out. By pulling the one strand thick samples apart, the weld strength can be evaluated. In addition, polarized optical microscopy was performed to analyze process-induced morphological changes. Finally, correlations between the thermal history, morphology and mechanical properties of 3D-printed semi-crystalline polymers were made.