(694d) Effect of Layer Density on Irreversible Thermal Expansion and Interlayer Strength in Additively Manufactured Acrylonitrile Butadiene Styrene

Additive manufacturing (AM) has drawn interest from fields ranging from aerospace to tissue engineering and regenerative medicine (TERM) to metamaterials. With AM, specimens with complex internal geometries and tailorable structures can be manufactured. Despite the advantages and interest, broader use of AM is limited by poor mechanical properties, lack of reliable part printing, and lack of expertise in AM. In many cases, AM parts have inferior properties to identical parts made with traditional manufacturing methods and exhibit poor interlayer bonding and residual stress. Additionally, understanding the processing-structure-properties relationship is critically important to ensure reproducible, reliable parts. More fully understanding these relationships may lead to parts with comparable, and ultimately superior, properties as well as additional functionalities with less manufacturing waste. In this work, the impact of layer density on physical and mechanical properties of additively manufactured parts was explored. Specifically, acrylonitrile butadiene styrene (ABS) samples were printed using fused deposition modeling (FDM) at several layer heights and their irreversible thermal expansion, tensile strength, and flexural strength were measured. Irreversible thermal strain increases with increasing layer density, up to 21% strain. Tensile and flexural strength exhibited the same behavior, with maxima at a layer density of 5 mm^-1. While residual thermal stress increases with increasing layer density, macroscale print quality increases with increasing layer density. These competing phenomena resulted in the observed maxima in mechanical properties related to interlayer bonding. The results of this work have significant implications for the application of additively manufactured polymers, both in terms of quality control and for tailorable mulitfunctionality.