Effects of Print Direction on the Mechanical Properties of 3D Printed Polymer Composites

For polymeric additive manufacturing (AM), print direction is an important processing parameter for the mechanical reliability of the inkjet 3D printed multi-material. To fully exploit AM potential in fabricating polymeric composites, a solid understanding of this factor during printing processes is in an urgent need.  The purpose of this study is to evaluate the influences of printing direction on the mechanical properties of 3D printed multi-material polymeric composites. The printing direction is defined via the angle of the specimens with respect to the movement of the print head. Specimens of stratified composites with various layer thickness are designed and fabricated via a multi-material 3D printer (Stratasys Connex3). Mechanical experiments are conducted to evaluate how the layer thickness and printing directions jointly influence the overall mechanical properties of the designs. Digital Image Correlation (DIC) is used to track the local and overall strain of the specimens during deformation.  This project also studied and quantified the variation in mechanical quality across multi-material 3D printed samples interfaces for different building direction using instrumented indentation testing (nanoindentation).  The findings in this work present an important step towards understanding the microstructural mechanics and properties of such 3D printed parts, which allow designers and engineers to better predict and model these materials.