# A New Approach in the Design of Microstructured Ultralight Components to Achieve Maximum Functional Performance

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## Abstract

**:**

## 1. Introduction

## 2. Design of Replicative Structures

## 3. L-PBF Process Parameters

- Laser size diffraction test—ASTM B822:
- -
- Dv (10) = 26 µm; 10% of powder volume has a diameter of less than 26 µm.
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- Dv (50) = 37 µm; the center of the volume distribution in volume is 37 µm.
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- There is no dust below 15 µm in volume.

- Sieve analysis test—ASTM B214:
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- No dust above 45 µm by weight.

## 4. Microstructures Performance Results

#### 4.1. Performance under Compressive Loads

- Stiffness/Weight = (F/δ)/W. This can be calculated from FEM and experimentally, considering elastic behavior of the structures.
- Maximum load before collapsing/weight: Fmax/W. This was calculated experimentally, being the final criteria when structures are on the verge of being crushed under load.

^{3}, 15.6 g mass and suffering 2 × 10

^{−2}mm of directional deformation in the z axis), is around 6.54 × 10

^{−3}. The relation Young Module/structure weight (Gpa/kg), is around 2.56 × 10

^{5}for the microstructure, and is 13.5 for the solid geometry. So, considering geometry and material analysis in the ratios load/weight and Young Module/weight, it can be said that studied microstructure presents 20,000 times better behavior that the solid microstructure.

#### 4.2. Experimental Performance

#### 4.3. Design of Complex Pieces: “Fitting Factor” Factor

## 5. Discussion

^{^2}(H2020-FETOPEN-2018-2019-2020-01 ADAM2 PROJECT) project.

## 6. Conclusions

- A methodology for the design and manufacturing of micro-structured ultralight components to achieve maximum functional performance is stablished.
- Design considerations for microstructures are stated. Component design is based on making replicas of the same structures, using octahedrons cells, from the smallest to the biggest scales.
- Manufacturing process parameters for microstructured ultralight components using Laser Powder Bed Fusion (L-PBF) technology are defined. Specific data for the cases studied are presented, and the boundaries in the print constraints are shown.
- Component behavior regarding compressive loads, and stress and strain distribution performance is analyzed by finite element simulation and experimental validation. Considering geometry and material analysis in the ratios load/weight and Young Module/weight (Section 4.1), it can be said that studied microstructure presents 20,000 times better behavior that the solid microstructure.
- A “fitting factor” in order to consider the difference between the designed part and the manufactured part due to the intrinsic characteristics of the L-PBF manufacturing process is considered. This factor is based on the bar diameter that affects stiffness in the third order, which is a very sensitive parameter. This method presents the correlation of FEM to real printing structures, which is easily done by a factor affecting bar diameter.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Acknowledgments

## Conflicts of Interest

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**Figure 2.**Three different scales of the structure. (

**Left**) First Scale: small octahedron (“cell”), (

**Center**) Second scale: octaedron lattices, (

**Right**) Third scale: octahedron structure.

**Figure 3.**(

**a**) Printed geometries for parameter tests. (

**b**) Zoom on printed geometry for parameter tests. (

**c**) Printed geometries organized according to tested parameters.

**Figure 4.**Printed workpieces. (

**Left**) Microstructure printed with 150 W laser power and 35 µs of exposure time. (

**Center**) Microstructure printed with 150 W laser power and 50 µs of exposure time. (

**Right**) Microstructure printed with 150 W laser power and 65 µs of exposure time.

**Figure 7.**(

**a**) Single octahedron design, (

**b**) Octahedron microstructure bar made of 9 octahedrons, (

**c**) 6 octahedrons microstructure, (

**d**) Big octahedron microstructure made of octahedron bars and octahedron cells.

**Figure 8.**(

**a**) Octahedron microstructure latice made of nine octahedrons, (

**b**) 6 octahedrons microstructure, (

**c**) octahedron microstructure made of octahedron lattice.

**Figure 9.**Two heat treatments suitable for IN718 [22].

**Figure 11.**(

**Left**) Designed structure for experimental validation. (

**Right**) Real structure for experimental validation.

Ni | Cr | Fe | Cb | Mb | Co | Al | Ti | Si | Mn | C |
---|---|---|---|---|---|---|---|---|---|---|

52.82 | 19.0 | 17.0 | 5.0 | 3.0 | 1.0 | 0.8 | 0.6 | 0.35 | 0.35 | 0.08 |

Design Parameters | Value |
---|---|

Bars length (mm) | 0.7 |

Bars radius (mm) | 0.01 |

Number of octahedrons | 9 |

Laser Power (W) | 150 | 200 | 250 | 300 | 350 | 400 |

Exposure Time (µs) | 20 | 35 | 50 | 65 | 80 | 95 |

Process Parameters | Value |
---|---|

Laser power (W) | 150 |

Exposure time (µs) | 55 |

Properties | Geometry a | Geometry b | Geometry c | Geometry d |
---|---|---|---|---|

Volume (mm^{3}) | 4.4 × 10^{−4} | 5.278 × 10^{−3} | 7.1 × 10^{−3} | 4.2 |

Mass (g) | 3.6 × 10^{−7} | 4.3 × 10^{−3} | 5.8 × 10^{−3} | 3.4 × 10^{−4} |

Directional deformation (Z axis) (mm) | −7.51 × 10^{−3} | −9.02 × 10^{−7} | −2.5 × 10^{−3} | −2.32 × 10^{−3} |

Minimun combined stress (MPa) | −6.5 × 10^{5} | −9.06 × 10^{3} | −3.75 × 10^{3} | −2.21 × 10^{5} |

Maximun combined stress (MPa) | 6.09 × 10^{5} | 8.7 × 10^{3} | 1.01 × 10^{5} | 2.05 × 10^{3} |

Load/Weight | 1.24 × 10^{2} | 2.36 × 10^{−2} | 1.75 × 10^{−2} | 1.24 × 10^{2} |

Relation (Gpa/kg) = Young Module/Weigth | 2.56 × 10^{5} | 4.86 × 10^{1} | 3.61 × 10^{1} | 2.56 × 10^{5} |

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**MDPI and ACS Style**

Calleja-Ochoa, A.; Gonzalez-Barrio, H.; López de Lacalle, N.; Martínez, S.; Albizuri, J.; Lamikiz, A.
A New Approach in the Design of Microstructured Ultralight Components to Achieve Maximum Functional Performance. *Materials* **2021**, *14*, 1588.
https://doi.org/10.3390/ma14071588

**AMA Style**

Calleja-Ochoa A, Gonzalez-Barrio H, López de Lacalle N, Martínez S, Albizuri J, Lamikiz A.
A New Approach in the Design of Microstructured Ultralight Components to Achieve Maximum Functional Performance. *Materials*. 2021; 14(7):1588.
https://doi.org/10.3390/ma14071588

**Chicago/Turabian Style**

Calleja-Ochoa, Amaia, Haizea Gonzalez-Barrio, Norberto López de Lacalle, Silvia Martínez, Joseba Albizuri, and Aitzol Lamikiz.
2021. "A New Approach in the Design of Microstructured Ultralight Components to Achieve Maximum Functional Performance" *Materials* 14, no. 7: 1588.
https://doi.org/10.3390/ma14071588