yu wang

Anisotropy on strength between different layers and filaments in the material extrusion (MEX) process has a significant influence on mechanical performances of fabricated objects. A novel theory and methodology is proposed to improve mechanical performances of parts by designing and controlling the anisotropy. Anisotropy can then be in alignment with load paths under the guidance of force-flow. In this study, by (1) dividing the part into several building areas and generating corresponding building direction considering the force-flow properties of the part; (2) generating novel toolpaths which are based on principal stress lines (PSL) and will map the direction and magnitude of PSL, the adverse influence of anisotropy on mechanical performances between different layers and filaments can be minimized respectively. A 6-axis robot arm integrated with an extrusion system is constructed to handle the multi-direction building of each building area. The study will advance the development of additive manufacturing from "prototype" to "end-use".

： Systematically discusses the state-of-the-art research of parts design for additive manufacturing from the aspects of structure design with topology optimization， mesoscopic structure， parts integration， fluid pipeline and heat exchanger，and the aspects of process planning with toolpaths，buliding direction，multi-axis construction and curved layers. On this basis，AM parts integration design， multi-scale heterogeneous cellular structure design，performance-oriented process planning and process planning for continuous carbon fiber reinforced composites as the potential development directions were proposed.

• A design optimization method of lattice structure coupling constraints and an-isotropy of AM was proposed. • The superiority of the lattice structure based on principal stress lines was verified by finite element analysis. • The anisotropy model was established based on FDM specimens with different diameters and deposition orientations. • The strength and stiffness of the optimized cantilever beam with heterogeneous conformal lattice structure were improved. Replacing solid structures with lattice structure is a way enabled by additive manufacturing (AM) to realize part lightweight design. Conventional design optimization method based on homogeneous periodic lattice structure cannot achieve the optimal structure without taking the stress magnitude and orientation into account. A design optimization method of heterogeneous conformal lattice structure coupling constraints and anisotropy of AM based on principal stress lines (PSL) is proposed. (1) The PSL is calculated based on finite element analysis to visualize the path of load transfer. (2) The load-adapted lattice structure is generated guided by the PSL. (3) In order to further optimize lattice structure, the lattice structure optimization model is established by coupling an-isotropy and constraints of AM based on the fused deposition modeling (FDM) experiment. Taking a cantilever beam as a case, the maximum force-to-weight ratio and the stiffness-to-weight ratio of the optimized heterogeneous conformal lattice structure are increased by 11.8% and 41.8% respectively compared with homogeneous conformal lattice structure, which verified the feasibility of the proposed method.

3D concrete printing has received worldwide attention while the development on new cementitious material compositions for 3D printing is inadequate. This study employed the recycled sand instead of natural sand to achieve 3D concrete printing and investigated the hardened properties of this extrusion-based material. The effect of replacement ratio of recycled sand, curing age, nozzle height and anisotropic behavior were evaluated based on the compressive tests, tensile splitting tests and flexural tests. Moreover, the digital image correlation (DIC) technique was adopted to capture the strain behavior and failure pattern of this layered and printed concrete. Owing to the high un-hydrated cement paste attached to the recycled sand and the internal curing mechanism, the compressive and flexural strengths of the 3D printed concrete with recycled sand were a little lower than those specimens without recycled sand. The compressive, tensile splitting and flexural strength of 3D printed concrete with recycled sand had obvious anisotropy. The replacement of recycled sand had limited effect on the anisotropy of compressive and flexural strength, but had certain effect on the tensile splitting strength. Since recycled sand is one of those major products derived from the construction and demolition waste, it is believed that the employment of recycled sand to the mix of 3D printed concrete will significantly improve the sustainability of 3D printed concrete structures.

Anisotropy on strength between different layers and filaments in the material extrusion (MEX) process has a significant influence on mechanical performances of fabricated objects. A novel theory and methodology is proposed to improve mechanical performances of parts by designing and controlling the anisotropy. Anisotropy can then be in alignment with load paths under the guidance of force-flow. In this study, by (1) dividing the part into several building areas and generating corresponding building direction considering the force-flow properties of the part; (2) generating novel toolpaths which are based on principal stress lines (PSL) and will map the direction and magnitude of PSL, the adverse influence of anisotropy on mechanical performances between different layers and filaments can be minimized respectively. A 6-axis robot arm integrated with an extrusion system is constructed to handle the multi-direction building of each building area. The study will advance the development of additive manufacturing from "prototype" to "end-use".

Anisotropy on strength between different layers and filaments in the material extrusion (MEX) process has a significant influence on mechanical performances of fabricated objects. A novel theory and methodology is proposed to improve mechanical performances of parts by designing and controlling the anisotropy. Anisotropy can then be in alignment with load paths under the guidance of force-flow. In this study, by (1) dividing the part into several building areas and generating corresponding building direction considering the force-flow properties of the part; (2) generating novel toolpaths which are based on principal stress lines (PSL) and will map the direction and magnitude of PSL, the adverse influence of anisotropy on mechanical performances between different layers and filaments can be minimized respectively. A 6-axis robot arm integrated with an extrusion system is constructed to handle the multi-direction building of each building area. The study will advance the development of additive manufacturing from "prototype" to "end-use".