A new boundary interlock geometry design pattern to strengthen FDM part multi-material interface

Abstract

Multi-material Fused Deposition Modeling (FDM) enables the realization of designs in complex geometries with multiple materials. However, achieving an adequate level of interfacial bonding strength between different materials remains a significant challenge. Other than addressing this challenge through material bonding at molecular scale or optimizing the printing parameters, new design methodologies also pose good potential. This work studied the mechanical properties of multi-material printed objects, with a particular focus on the interface zone built between the various materials at their geometrical borders. Four types of test samples were designed, printed, and tested: (A) single-material test samples uni-body (without boundary interface); (B) single-material test samples with planar boundary interface; (C) bi-material test samples with a planar boundary interface; and (D) bi-material test samples with new boundary interlock geometry design interface. The comparison of the mechanical performance between Type-A, -B, and -C test samples demonstrated the influence of the presence of a geometrical boundary interface between the same material and different materials. The comparison between Type-C and -D demonstrated the impact of introducing boundary interlock geometry. This study showed that with the new boundary interlock geometry design, the mechanical strength (tensile strength) of multi-material prints can be greatly improved. Furthermore, a Design of Experiment is conducted to identify the interlock geometry design parameters optimized for tensile strength. This work proves the significance of boundary interlock geometry design in multi-material printing and provides a methodology to explore new boundary interlock geometry design patterns to strengthen the FDM part multi-material interface.