Development of Intertwined Infills to Improve Multi-Material Interfacial Bond Strength

Multi-material additive-manufacturing (MMAM) technology provides a solution to 3D print a variety of parts consisting of multiple materials without the necessity of performing complex manufacturing processes. Till now various MMAM techniques have been developed for different applications. The wide availability of materials and recent developments in MMAM has opened doors for innovation in producing truly functional products using various materials. A lot of research is research going on in developing efficient 3D printers for MMAM, but conventional software tools does not full-fill the modern requirements suited for 3D printing of multi-material structures. There is an existing research gap between existing CAD tools, 3D printers and slicing software 3D printing of multi-material parts. One major concern of MMAM is the strength at the interface between materials. Based on the observation of how nature puts materials together, this research develops an initial hypothesis that if the materials are overlapped and interlaced with each other, the interface bonding strength will be enhanced. To test this hypothesis, a computer-aided manufacturing (CAM) tool that can process overlapped material regions is needed. However, existing computational tools lack key multi-material design processing features and have certain limitations in making full use of material information, which restricts the test of the hypothesis. Therefore, this research also develops a new MMAM slicing framework that efficiently identifies the multi-material regions and develops interlaced infills. Based on ray-tracing technology, layered depth material images (LDMI) is developed to process the material information from computer-aided design (CAD) models for tool-path planning. Each sample point in the LDMI has an associated material and geometric properties that are used to recover the material distribution in each slice. In this research, an interlocking joint (T-joint) and an interlacing infill are developed in the regions with multiple materials. By carrying out tensile tests, it is shown that the proposed infill outperforms the interlocking joint, and a fracture occurs even outside the joint area. This validates the initial hypothesis, and the enhancement of interface strength is achieved by overlapping and interlacing materials.