Additive manufacturing of stiff and strong structures by leveraging printing-induced strength anisotropy in topology optimization
Additive manufacturing of stiff and strong structures by leveraging printing-induced strength anisotropy in topology optimization
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DOI：
10.1016/j.addma.2023.103730
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发表时间：
2023-08
影响因子：
11
通讯作者：
R. Kundu;X. Zhang
中科院分区：
文献类型：
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作者：
R. Kundu;X. Zhang
在增材制造（AM）中，特别是在材料挤压过程中，各向异性在决定实际结构性能（包括打印部件的刚度和强度）方面起着至关重要的作用。除非加以考虑，否则各向异性会损害拓扑优化结构的客观性能，并导致应力敏感设计领域的过早失效。本研究利用基于材料挤压的3D打印工艺诱导的各向异性，使用两步框架设计和制造刚性，坚固和轻质结构。首先，在假设各向异性（即横向各向同性）和各向同性填充类型作为候选材料相的情况下，基于am取向的各向异性强度拓扑优化公式优化了结构几何形状和填充方向。公式中不同的刚度和强度插值方案允许各向异性和各向同性材料相在设计域中的优化分配，同时满足各自的Tsai-Wu和von Mises应力约束。其次，合适的制造方法可以实现各向异性和各向同性的材料相，具有适当的填充密度，可控制的打印路径（即填充方向），以及不同材料相的强界面。实验研究表明，优化和制造的结构刚度提高37%，单位质量强度提高100%。基于各向异性强度的优化通过沿应力路径的同时充填排列和对高应力集中的拓扑适应来提高承载能力。采用的界面制造方法以最小的额外材料用量和多轴填充模式加强了相对较弱的各向异性接缝。此外，数值预测的失效位置与实验观测结果一致。所展示的框架是通用的，可以潜在地用于其他表现出各向异性的增材制造工艺，如纤维复合材料。
Anisotropy in additive manufacturing (AM), particularly in the material extrusion process, plays a crucial role in determining the actual structural performance, including the stiffness and strength of the printed parts. Unless accounted for, anisotropy can compromise the objective performance of topology-optimized structures and allow premature failures for stress-sensitive design domains. This study harnesses process-induced anisotropy in material extrusion-based 3D printing to design and fabricate stiff, strong, and lightweight structures using a two-step framework. First, an AM-oriented anisotropic strength-based topology optimization formulation optimizes the structural geometry and infill orientations, while assuming both anisotropic (i.e., transversely isotropic) and isotropic infill types as candidate material phases. The dissimilar stiffness and strength interpolation schemes in the formulation allow for the optimized allocation of anisotropic and isotropic material phases in the design domain while satisfying their respective Tsai–Wu and von Mises stress constraints. Second, a suitable fabrication methodology realizes anisotropic and isotropic material phases with appropriate infill density, controlled print path (i.e., infill directions), and strong interfaces of dissimilar material phases. Experimental investigations show up to 37% improved stiffness and 100% improved strength per mass for the optimized and fabricated structures. The anisotropic strength-based optimization improves load-carrying capacity by simultaneous infill alignment along the stress paths and topological adaptation in response to high stress concentration. The adopted interface fabrication methodology strengthens comparatively weaker anisotropic joints with minimal additional material usage and multi-axial infill patterns. Furthermore, numerically predicted failure locations agree with experimental observations. The demonstrated framework is general and can potentially be adopted for other additive manufacturing processes that exhibit anisotropy, such as fiber composites.