Manufacturing Issues and the Resulting Complexity in Modeling of Additively Manufactured Metallic Microlattices

Although metallic microlattice material is a sought after research topic currently, it suffers from manufacturing defects such as micro-voids formation due to missed fusion, stemmed from the stacking-layered-fused nature of the metal powder in Powder Bed Fusion (PBF) process. These defects result in weakening of the finished part and reduced mechanical performance under service load, possibly leading to low fatigue strength, and raise serious question about 3D printed structural integrity. Numerical simulation of the built parts also becomes difficult due to irregular physical properties including geometry and anisotropic nature of mechanical properties. This paper provides an overview on the manufacturing issues and the subsequent hurdle faced in numerical simulation of metallic microlattices. While the issues in manufacturing are related to emerging additive manufacturing techniques and out of control of end users, it has been suggested that the limitations in numerical simulation can be overcome by employing advanced approaches, in both physical properties measurement and modeling.

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EXPERIMENTAL INVESTIGATION AND SIMULATION OF 3D-PRINTED LATTICE STRUCTURES

Acta Polytechnica CTU Proceedings ◽

10.14311/app.2019.25.0052 ◽

2019 ◽

Vol 25 ◽

pp. 52-57

Author(s):

Eva Heiml ◽

Anna Kalteis ◽

Zoltan Major

Keyword(s):

Mechanical Performance ◽

Bulk Material ◽

Deformation Behaviour ◽

Lightweight Design ◽

Thermoplastic Polyurethane ◽

Selective Laser Sintering ◽

Structural Performance ◽

Lattice Structures ◽

3D Printed ◽

Manufacturing Techniques

Lattice structures are currently of high interest, especially for lightweight design. They generally have better structural performance per weight than parts made of bulk material. With conventional manufacturing techniques they are diﬃcult to produce, but with additive manufacturing (AM) fabricationisfeasible. To better understand their behaviour under various loading conditions two lattice structures in diﬀerent conﬁgurations were observed. For each structure three diﬀerent test specimens were designed and manufactured using selective laser sintering (SLS). To investigate the mechanical performance under large deformations the specimens were made of a thermoplastic polyurethane(TPU), which shows a hyperelastic material behaviour. Beside the experimental observations also ﬁnite element analyses (FEA) were conducted to investigate the deformation behaviour in more detail.

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The Influence of Process Parameters and Build Orientation on the Creep Behaviour of a Laser Powder Bed Fused Ni-based Superalloy for Aerospace Applications

Materials ◽

10.3390/ma12091390 ◽

2019 ◽

Vol 12 (9) ◽

pp. 1390 ◽

Cited By ~ 6

Author(s):

Hani Hilal ◽

Robert Lancaster ◽

Spencer Jeffs ◽

John Boswell ◽

David Stapleton ◽

...

Keyword(s):

Process Parameters ◽

Structural Integrity ◽

Mechanical Performance ◽

Creep Behaviour ◽

Test Method ◽

Influence Of Process Parameters ◽

Powder Bed ◽

Build Orientation ◽

Aerospace Applications ◽

Layer Manufacturing

Additive Layer Manufacturing (ALM) is an innovative net shape manufacturing technology that offers the ability to produce highly intricate components not possible through traditional wrought and cast procedures. Consequently, the aerospace industry is becoming ever more attentive in exploiting such technology for the fabrication of nickel-based superalloys in an attempt to drive further advancements within the holistic gas turbine. Given this, the requirement for the mechanical characterisation of such material is rising in parallel, with limitations in the availability of material processed restricting conventional mechanical testing; particularly with the abundance of process parameters to evaluate. As such, the Small Punch Creep (SPC) test method has been deemed an effective tool to rank the elevated temperature performance of alloys processed through ALM, credited to the small volumes of material utilised in each test and the ability to sample material from discrete locations. In this research, the SPC test will be used to assess the influence of a number of key process variables on the mechanical performance of Laser Powder Bed Fused (LPBF) Ni-based superalloy CM247LC. This will also include an investigation into the influence of build orientation and post-build treatment on creep performance, whilst considering the structural integrity of the different experimental builds.

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Voids in fiber-reinforced polymer composites: A review on their formation, characteristics, and effects on mechanical performance

Journal of Composite Materials ◽

10.1177/0021998318772152 ◽

2018 ◽

Vol 53 (12) ◽

pp. 1579-1669 ◽

Cited By ~ 70

Author(s):

Mahoor Mehdikhani ◽

Larissa Gorbatikh ◽

Ignaas Verpoest ◽

Stepan V Lomov

Keyword(s):

Mechanical Performance ◽

Void Formation ◽

Thermomechanical Properties ◽

Research Field ◽

Liquid Composite Molding ◽

Fiber Reinforced ◽

Manufacturing Defects ◽

Advantages And Disadvantages ◽

Mechanical Effects ◽

Manufacturing Techniques

Voids, the most studied type of manufacturing defects, form very often in processing of fiber-reinforced composites. Due to their considerable influence on physical and thermomechanical properties of composites, they have been extensively studied, with the focus on three research tracks: void formation, characteristics, and mechanical effects. Investigation of voids in composites started around half a century ago and is still an active research field in composites community. This is because of remaining unknowns and uncertainties about voids as well as difficulties in their suppression in modern manufacturing techniques like out-of-autoclave curing and parts with high complexity, further complicated by increased viscosity of modified resins. Finally, this is because of the increasing interest in realization of more accurate void rejection limits that would tolerate some voidage. The current study reviews the research on formation, characterization, and mechanical effects of voids, which has been conducted over the past five decades. Investigation and control of void formation, using experimental and modeling approaches, in liquid composite molding as well as in prepreg composite processing are surveyed. Techniques for void characterization with their advantages and disadvantages are described. Finally, the effect of voids on a broad range of mechanical properties, including inter-laminar shear, tensile, compressive, and flexural strength as well as fracture toughness and fatigue life, is appraised. Both experimental and simulation approaches and results, concerning voids' effects, are reviewed.

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Mechanical Performance of 3D-Printed Biocompatible Polycarbonate for Biomechanical Applications

Polymers ◽

10.3390/polym13213669 ◽

2021 ◽

Vol 13 (21) ◽

pp. 3669

Author(s):

Giovanni Gómez-Gras ◽

Manuel D. Abad ◽

Marco A. Pérez

Keyword(s):

Mechanical Performance ◽

Cost Savings ◽

Bone Scaffold ◽

Fused Filament Fabrication ◽

Synthetic Materials ◽

3D Printed ◽

Biomedical Industry ◽

Manufacturing Techniques ◽

Manufacturing Time ◽

Printing Parameters

Additive manufacturing has experienced remarkable growth in recent years due to the customisation, precision, and cost savings compared to conventional manufacturing techniques. In parallel, materials with great potential have been developed, such as PC-ISO polycarbonate, which has biocompatibility certifications for use in the biomedical industry. However, many of these synthetic materials are not capable of meeting the mechanical stresses to which the biological structure of the human body is naturally subjected. In this study, an exhaustive characterisation of the PC-ISO was carried out, including an investigation on the influence of the printing parameters by fused filament fabrication on its mechanical behaviour. It was found that the effect of the combination of the printing parameters does not have a notable impact on the mass, cost, and manufacturing time of the specimens; however, it is relevant when determining the tensile, bending, shear, impact, and fatigue strengths. The best combinations for its application in biomechanics are proposed, and the need to combine PC-ISO with other materials to achieve the necessary strengths for functioning as a bone scaffold is demonstrated.

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The Effect of a Phase Change on the Temperature Evolution during the Deposition Stage in Fused Filament Fabrication

Computers ◽

10.3390/computers10020019 ◽

2021 ◽

Vol 10 (2) ◽

pp. 19

Author(s):

Sidonie F. Costa ◽

Fernando M. Duarte ◽

José A. Covas

Keyword(s):

Phase Change ◽

Energy Equation ◽

Mechanical Performance ◽

Amorphous Material ◽

Acrylonitrile Butadiene Styrene ◽

Fused Filament Fabrication ◽

Crystalline Polymers ◽

3D Printed ◽

Manufacturing Techniques ◽

Butadiene Styrene

Additive Manufacturing Techniques such as Fused Filament Fabrication (FFF) produce 3D parts with complex geometries directly from a computer model without the need of using molds and tools, by gradually depositing material(s), usually in layers. Due to the rapid growth of these techniques, researchers have been increasingly interested in the availability of strategies, models or data that may assist process optimization. In fact, 3D printed parts often exhibit limited mechanical performance, which is usually the result of poor bonding between adjacent filaments. In turn, the latter is influenced by the temperature field history during deposition. This study aims at evaluating the influence of the phase change from the melt to the solid state undergone by semi-crystalline polymers such as Polylactic Acid (PLA), on the heat transfer during the deposition stage. The energy equation considering solidification is solved analytically and then inserted into a MatLab® code to model cooling in FFF. The deposition and cooling of simple geometries is studied first, in order to assess the differences in cooling of amorphous and semi-crystalline polymers. Acrylonitrile Butadiene Styrene (ABS) was taken as representing an amorphous material. Then, the deposition and cooling of a realistic 3D part is investigated, and the influence of the build orientation is discussed.

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CARPENTER 883 PLUS

Alloy Digest ◽

10.31399/asm.ad.ts0529 ◽

1994 ◽

Vol 43 (7) ◽

Keyword(s):

Fracture Toughness ◽

Physical Properties ◽

Tensile Properties ◽

Structural Integrity ◽

Heat Treating ◽

Die Steel ◽

Aisi Type ◽

Red Hardness ◽

Hot Work Die

Abstract CARPENTER 883 PLUS is a 5% Chromium hot work die steel designed for applications requiring both toughness and good red-hardness. It achieves this with higher purity, homogeneity and greater structural integrity than standard AISI type H13. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on forming, heat treating, and machining. Filing Code: TS-529. Producer or source: Carpenter. See also Alloy Digest TS-469, January 1987.

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