Investigation of process-structure-property relationships in polymer extrusion based additive manufacturing through in situ high speed imaging and thermal conductivity measurements

Additive manufacturing has gained significant research attention due to multiple advantages over traditional manufacturing technologies. A fundamental understanding of the relationships between process parameters, microstructure and functional properties of built parts is critical for optimizing the additive manufacturing process and building parts with desired properties. This is also critical for a multi-functional part where the process needs to be optimized with respect to disparate performance requirements such as mechanical strength and thermal conductivity. This paper presents in situ high speed imaging and build-direction thermal conductivity measurements of polymer extrusion based additively manufactured parts in order to understand the effect of process parameters such as raster speed, infill percentage and layer height on build-direction thermal conductivity. Measurements of thermal conductivity using a one-dimensional heat flux method are correlated with in situ process images obtained from a high speed camera as well as cross section images of the built part. Results indicate strong dependence of build-direction thermal conductivity on raster speed, layer thickness and infill percentage, which is corroborated by high speed imaging of the printing process at different values of these process parameters. Key trade-offs between process throughput and thermal properties are also identified. In addition to enhancing our fundamental understanding of polymer extrusion based additive manufacturing and its influence on thermal properties of built parts, results presented here may facilitate process optimization towards parts with desired thermal and multi-functional properties.