LPBF Manufactured Functionally Graded Lattice Structures Obtained by Graded Density and Hybrid Poisson’s Ratio

Abstract

The additive manufacturing (AM) of innovative lattice structures with unique mechanical properties has received widespread attention due to the capability of AM processes to fabricate freeform and intricate structures. The most common way to characterize the additively manufactured lattice structures is via the uniaxial compression test. However, although there are many applications for which lattice structures are designed for bending (e.g., sandwich panels cores and some medical implants), limited attention has been paid toward investigating the flexural behavior of metallic AM lattice structures with tunable internal architectures. The purpose of this study was to experimentally investigate the flexural behavior of AM Ti-6Al-4V lattice structures with graded density and hybrid Poisson’s ratio (PR). Four configurations of lattice structure beams with positive, negative, hybrid PR, and a novel hybrid PR with graded density were manufactured via the laser powder bed fusion (LPBF) AM process and tested under four-point bending. The manufacturability, microstructure, micro-hardness, and flexural properties of the lattices were evaluated. During the bending tests, different failure mechanisms were observed, which were highly dependent on the type of lattice geometry. The best response in terms of absorbed energy was obtained for the functionally graded hybrid PR (FGHPR) structure. Both the FGHPR and hybrid PR (HPR) structured showed a 78.7% and 62.9% increase in the absorbed energy, respectively, compared to the positive PR (PPR) structure. This highlights the great potential for FGHPR lattices to be used in protective devices, load-bearing medical implants, and energy-absorbing applications.

Improved mechanical performance of quasi-cubic lattice metamaterials with asymmetric joints

“…The elasto-plastic response of material was defined with the isotropic hardening and linear hardening low. The erosion condition for the finite elements was defined according to the maximum tensile pressure criterion 35,57,58 . This criterion is recommended by the explicit materials library of ANSYS for different polymeric materials and in our previous work we found that this criterion provided good agreement with experimental data 33 .…”

“…The considered design method has its origin in the so-called pantographic metamaterials 4,18,34,35 . These type of metamaterials consist of two families of the inclined beams placed with the offsets and interconnected at the intersections by the small pivots 36 .…”

Experimental Evaluation of the Effects of Discrete-Grading-Induced Discontinuities on the Material Properties of Functionally Graded Ti-6Al-4V Lattices

“…Recent developments in additive manufacturing (AM) and selective laser melting (SLM) using biocompatible Ti-6Al-4V (Ti64) powder have expanded the applications of metal AM to medical implants. This advancement is primarily attributed to AM's capability to produce complex geometries that were not possible using conventional subtractive manufacturing [1][2][3][4]. Additively manufactured patient-specific medical devices have the benefit of matching individual patient's bone anatomy due to the high customizability of AM process [5][6][7].…”

Properties Evaluations of Topology Optimized Functionally Graded Lattice Structures Fabricated by Selective Laser Melting

“…Therefore, in ensuring the designed structure meets the strength requirements while saving as much materials as possible, the relative density is designed differently in various regions. To date, most research interests involving this FGLSs using SLM fabrication have been concentrated on the effects of cellular structural types and metallic types on mechanical properties [ 13 , 14 , 15 , 16 , 17 ]. Mingkang Zhang et al [ 18 ] designed and fabricated body-center-cubic (BCC) FGLSs based on Ti6Al4V alloy.…”