Predicting failure modes of 3D-printed multi-material polymer sandwich structures from process parameters

The emergence of additive manufacturing (AM) technologies, such as fused deposition modeling (FDM), have enabled the realization of structures with superior mechanical performance through lightweighting and multi-material architectures. However, the complexity associated with the internal geometric features and potential material configurations have also presented new challenges in designing these structures to optimize mechanical performance. In particular, the failure mechanisms and their relationship to the load bearing capacity of the structures may vary compared to analogous structures designed using conventional manufacturing techniques. In this work, we investigate failure modes of 3 D-printed (3DP) multi-material polymer sandwich beam structures manufactured from acrylonitrile butadiene styrene (ABS) and polycarbonate (PC) materials and subjected to three-point bend loading. Digital Image Correlation (DIC) is utilized to understand the effects of different process parameters on the mechanical response of the 3DP structures. ABS and PC dogbone tensile specimens were printed to establish the baseline properties in tension with varying raster angles and infill patterns. Multi-material sandwich beam structures were then printed with honeycomb cores using different processing and architectural parameters, and the failure modes and loads of these structures were compared with predications from a failure model for sandwich structures that accounts for the following conventional failure modes: (1) indentation, (2) face sheet bending, (3) core bending, and (4) core shear. With minor changes in the processing and geometric parameters, failure modes could be shifted from the face sheets to core bending and core shear, as evidenced by the DIC strain field measurements, and the corresponding max load-to-weight ratios could be increased. Estimations of the tensile properties of the face sheets and core were found to be sufficiently accurate when combining classical lamination theory (CLT) and rule-of-mixtures (ROM) models, while the failure model also predicted the load bearing capacity and failure mode in three-point bending with reasonable accuracy.