Effect of Fillets on Mechanical Properties of Lattice Structures Fabricated Using Multi-Jet Fusion Technology.

Aamer Nazir,Ahmad-Bin Arshad,Chi-Pin Hsu,Jeng-Ywan Jeng

doi:10.3390/ma14092194

Abstract

Cellular structures with tailored topologies can be fabricated using additive manufacturing (AM) processes to obtain the desired global and local mechanical properties, such as stiffness and energy absorption. Lattice structures usually fail from the sharp edges owing to the high stress concentration and residual stress. Therefore, it is crucial to analyze the failure mechanism of lattice structures to improve the mechanical properties. In this study, several lattice topologies with fillets were designed, and the effects of the fillets on the stiffness, energy absorption, energy return, and energy loss of an open-cell lattice structure were investigated at a constant relative density. A recently developed high-speed AM multi-jet fusion technology was employed to fabricate lattice samples with two different unit cell sizes. Nonlinear simulations using ANSYS software were performed to investigate the mechanical properties of the samples. Experimental compression and loading–unloading tests were conducted to validate the simulation results. The results showed that the stiffness and energy absorption of the lattice structures can be improved significantly by the addition of fillets and/or vertical struts, which also influence other properties such as the failure mechanism and compliance. By adding the fillets, the failure location can be shifted from the sharp edges or joints to other regions of the lattice structure, as observed by comparing the failure mechanisms of type B and C structures with that of the type A structure (without fillets). The results of this study suggest that AM software designers should consider filleted corners when developing algorithms for generating various types of lattice structures automatically. Additionally, it was found that the accumulation of unsintered powder in the sharp corners of lattice geometries can also be minimized by the addition of fillets to convert the sharp corners to curved edges.

Highlights

IntroductionCellular structures with multifunctional properties are common in nature and have shown promise for applications in the automotive, biomedical, and aerospace industries
The strut diameter is different for each type of lattice unit cell to keep the relative density constant
Uniaxial compressive experiments and finite element analysis (FEA) were performed to investigate the stiffness and failure mechanism, and the energy absorption and loss were determined by performing loading–unloading experiments to obtain the energy absorption and energy return data, which were used to calculate the energy loss of each type of lattice structure

Summary

Introduction

Cellular structures with multifunctional properties are common in nature and have shown promise for applications in the automotive, biomedical, and aerospace industries. By using AM techniques, cellular structures with uniform, and/or nonuniform microstructures can be constructed to obtain the desired properties for a particular application [13,14]. AM techniques have many advantages over traditional manufacturing processes, including quicker and less costly manufacturing, no tooling or material waste, the capacity for customization and personalization, and the ability to manufacture complex geometries, such as cellular structures, without additional cost or difficulty [15]

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Results

Conclusion