Interfacial bonding during multi-material fused deposition modeling (FDM) process due to inter-molecular diffusion

Multi-material fused deposition modeling (FDM) is an effective tool to realize the optimal design and manufacturing with various materials, but how to achieve an adequate level of interfacial bonding strength between dissimilar materials is still a critical problem. Herein, the influence of three multi-material FDM processing parameters, i.e. nozzle temperature, building stage temperature and printing speed, on the interfacial bonding strength of thermoplastic polyurethane (TPU)/acrylonitrile butadiene styrene (ABS) bi-material structures was experimentally investigated. It was found that the interfacial bonding strength was significantly improved from 0.86 to 1.66 MPa (increased by 93%) when the building stage temperature increased from 30 to 68 degrees C, which was the most effective processing parameter. Then, a heat transfer-based polymer inter-molecular diffusion theory was developed to understand the interfacial bonding mechanism. The interfacial temperature profiles during multi-material FDM process were experimentally measured by inserting thermocouples into printing specimens, and the theoretical model was well validated due to the good agreement between experimental and numerical data of interfacial temperature and bonding strength. The model provided an accurate prediction of interfacial bonding strength based on the understanding of thermally-driven diffusion of multi-material filaments; which would help improving the mechanical properties of products fabricated by multi-material FDM. (c) 2018 Elsevier Ltd. All rights reserved.