Development of a design and characterization framework for fabrication of functionally graded materials using magnetic field-assisted digital light processing stereolithography

Abstract Functionally graded materials (FGMs) offer several advantages over traditional materials. Fabrication of FGMs via additive manufacturing (AM) processes would allow creating a part with a complex geometry while controlling the graded structure and has gained significant interest in the recent years. Magnetic field-assisted digital light processing (DLP) stereolithography is a promising technique to fabricate FGMs. However, it is still challenging to be able to fabricate FGMs with precisely controlled structures and properties. In this study, a design, manufacturing, and characterization framework is developed for using DLP to fabricate FGMs. In this work, a customized DLP printer with assisitve magnetic field is developed and used to fabricate polymeric composites with embedded magnetic particles. By varying the magnetic field, different gradients of particle concentration can be achieved. The particle distribution within the sample is characterized by nano-computed tomography and the greyscale analysis using optical microscopy. Nanoindentation is performed to measure the local material properties in the graded area. Standard tensile tests are also conducted on samples with preset particle contents, and the results are cross compared with nanoindentation results. A finite element model is developed to analyze the effect of magnetic flux density on the resulting particle content. Correlations between the magnetic flux density and particle content, and between the particle content and the local material behavior are shown, which form the foundation of the proposed framework. This framework provides a guided method for designers and manufacturers to create FGMs with more predictable results.