Robocasting of 3D-ceramic macrocellular structures with tubular filaments

拟议的项目侧重于调查材料的具体原则的自动铸造过程。该提案的主要目标是开发负载Al2O3，SiC和Si3N4的新型凝胶系统，用于复杂3D结构的增材制造。方法上的新奇是各种横截面的管状长丝的应用，这需要特殊的高粘度凝胶和挤出机喷嘴。研究主要集中在沉积时长丝的变形，这主要取决于外力和流变特性，如粘度，剪切弹性模量和屈服应力。对于高粘度凝胶的流变行为的研究是至关重要的，后者是强烈影响的挤出机喷嘴内的流动剖面，其中壁滑移和活塞流很可能发生。另一个目的是减少由于外力（重力、毛细管中的负压）引起的长丝变形，以实现近净形能力。此外，应获得高固体含量（> 50体积%）的凝胶以引起低干燥收缩。应验证挤出时形状演变的静态和动态模型，并使其适用于管状长丝。重要的是，应详细说明管状长丝结构与块状长丝结构在机械性能方面的差异。此外，陶瓷3D结构的机械性能应使用基于单根烧结细丝的机械性能的FEM进行模拟。

The proposed project focuses on the investigation of material-specific principles of the robocasting-process. The main goal of the proposal is to develop novel gel-systems loaded with Al2O3, SiC und Si3N4 for additive manufacturing of complex 3D-structures. The methodical novelty is the application of tubular filaments of various cross-sections, which require special high-viscosity-gels and extruder-nozzle. The investigation concentrates on the deformation of the filaments while deposition, which is predominately determined by external forces and rheological characteristics such as viscosity, shear-elastic-modulus and yield-stress. For highly viscous gels the study of the rheological behavior is of crucial importance; the latter is strongly influenced by the flow-profile within the extruder-nozzle, where wall slip and plug flow are likely to occur. A further objective is to diminish the deformation of the filaments due to external forces (gravity, under-pressure in the capillary) to achieve near-net-shape capability. Furthermore a high solids content (> 50 vol%) of the gels shall be attained to induce a low drying-shrinkage. Static and dynamic models for shape-evolution while extrusion shall be verified and adapted to tubular filaments, It is important to elaborate the differences between structures composed of tubular filaments compared to structures composed of massive filaments concerning mechanical properties. In addition, the mechanical properties of ceramic 3D Structures shall be simulated using FEM based on mechanical properties of single sintered filaments.