Measured and simulated mechanical properties of additively manufactured matrix-inclusion multimaterials fabricated by material jetting

Modern additive manufacturing enables the simultaneous processing of different materials during the printing process. While multimaterial 3D printing allows greater freedom in part design, the prediction of the mix-material properties becomes challenging. One type of multimaterials are matrix-inclusion composites, where one material contains inclusions of another material. Aim of this study was to develop a method to predict the uniaxial Young’s modulus and Poisson’s ratio of material jetted matrix-inclusion composites by a combination of simulations and experimental data. Fifty samples from commercially available materials in their pure and matrix-inclusion mixed forms, with cubic inclusions, have been fabricated using material jetting and mechanically characterized by uniaxial tensile tests. Multiple simulation approaches have been assessed and compared to the measurement results in order to find and validate a method to predict the multimaterials’ properties. Optical coherence tomography and microscopy was used to characterize the size and structure of the multimaterials, compared to the design. The materials exhibited Young’s moduli in the range of 1.4 GPa to 2.5 GPa. The multimaterial mixtures were never as stiff as the weighted volume average of the primary materials (up to 33.9 % softer for 45% RGD8530-DM inclusions in VeroClear matrix). Experimental data could be predicted by finite element simulations by considering a non-ideal contact stiffness between matrix and inclusion ( F A = 2.2 TN m 3 for RGD8530-DM , F A = 4.8 TN m 3 for RGD8430-DM ), and geometries of the printed inclusions that deviated from the design (rounded edge radii of r = 220 μ m). Not considering this would lead to a difference of the estimation result of up to 612 MPa (44%), simulating an inclusion volume fraction of 45% RGD8530-DM . Prediction of matrix-inclusion composites fabricated by multimaterial jetting printing, is possible, however, requires a priori knowledge or additional measurements to characterize non-ideal contact stiffness between the components and effective printed geometries, precluding therefore a simple multimaterial modelling.