# Spatial 3D Printing of Continuous Fiber-Reinforced Composite Multilayer Truss Structures with Controllable Structural Performance

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Design and Manufacturing

#### 2.1. Pyramid Truss Unit Design

#### 2.2. The Manufacture of Pyramid Truss Structure

#### 2.2.1. Material and Equipment

^{3}, breaking strength of 152 N, specific strength of 23.0 cN/dtex, modulus of 700 cN/dtex, from DuPont Corp) with excellent stability in 3D printing for CFRCs was used as the reinforcement material, and polylactide (PLA/1.75 mm, density of 1240 kg/m

^{3}) from Polymaker in China was used as the thermoplastic material.

#### 2.2.2. Pyramid Truss Manufacturing Process

## 3. Result and Discussion

#### 3.1. Single-Layer Pyramid Structure

#### 3.2. Multilayer Pyramid Structure

#### 3.3. Discussion

#### 3.3.1. Theoretical Analysis

#### 3.3.2. Failure Deformation Analysis

## 4. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 1.**Pyramid composite truss units and their different types of arrays stacked in 0/90°and 45° directions.

**Figure 2.**(

**a**) Continuous fiber composite 3D printer physical image, and (

**b**) continuous fiber composite space structure printing schematic.

**Figure 3.**Main errors of continuous fiber-composite-printed space truss structure: (

**a**) inclination angle error, (

**b**) lateral error of starting and landing point, and (

**c**) inter-layer error.

**Figure 4.**(

**a**) The 2 × 2 pyramidal truss unit structure samples, (

**b**) pyramidal truss structure samples of different scales, (

**c**) pyramidal truss structure samples of different tilt angles, (

**d**,

**f**) compressive curves with different truss inclination angles, and (

**g**,

**e**) compressive curves with different truss scales.

**Figure 5.**Samples of multilayer truss structure: (

**a**) vertically stacked three-layer truss sample (uniform structure design and non-uniform structure design per layer), and (

**b**) 45° connected stacked three-layer truss sample (uniform structure design and non-uniform structure design per layer).

**Figure 6.**Compression performance curves of different multilayer pyramid structures. (

**a**,

**b**) compression performance curves of vertically stacked three-layer truss sample (uniform structure design and non-uniform structure design per layer), and (

**c**,

**d**) ompression performance curves of 45° connected stacked three-layer truss sample (uniform structure design and non-uniform structure design per layer).

**Figure 7.**(

**a**) Actual photo of 2*2 pyramid truss unit compression, (

**b**) force analysis diagram of pyramid truss unit, (

**c**) force analysis of simplified pyramid single truss, and comparison of experimental data and theoretical peak force: (

**d**) different truss length and (

**e**) different inclination.

**Figure 8.**(

**a**) Compression failure performance of different structures, (

**b**) compression failure damage form of inclined trusses, and (

**c**) deformation in different stages.

Type | Inclination Angle θ | Truss Size L/mm | $\mathbf{Relative}\mathbf{Density}\overline{\mathit{\rho}}$ |
---|---|---|---|

A1 | 30° | 12 | 2.98% |

B1 | 35° | 2.81% | |

C1 | 40° | 2.74% | |

D1 | 45° | 2.76% | |

E1 | 50° | 2.88% | |

F1 | 55° | 3.11% | |

G1 | 60° | 3.48% | |

H1 | 65° | 4.06% |

Type | Inclination Angle θ | Truss Size L/mm | $\mathbf{Relative}\mathbf{Density}\overline{\mathit{\rho}}$ |
---|---|---|---|

A2 | 50° | 6 | 8.30% |

B2 | 8 | 5.46% | |

C2 | 10 | 3.86% | |

D2 | 12 | 2.88% | |

E2 | 14 | 2.23% | |

F2 | 16 | 1.78% | |

G2 | 18 | 1.45% |

Type | $\mathbf{The}\mathbf{Equivalent}\mathbf{Maximum}\mathbf{force}\mathbf{F}/\overline{\mathit{\rho}}$ (N) | $\mathbf{Equivalent}\mathbf{Strength}\mathsf{\sigma}$$/\overline{\mathit{\rho}}$ (MPa) | $\mathbf{Equivalent}\mathbf{Elastic}\mathbf{Modulus}\mathbf{E}/\overline{\mathit{\rho}}$ (MPa) |
---|---|---|---|

A1 | 1451.34 | 4.73 | 37.82 |

B1 | 2117.43 | 7.57 | 68.89 |

C1 | 2454.38 | 9.80 | 99.39 |

D1 | 2463.77 | 11.21 | 124.48 |

E1 | 2586.80 | 13.71 | 164.42 |

F1 | 2813.50 | 17.83 | 228.03 |

G1 | 2765.80 | 21.61 | 291.59 |

H1 | 2850.98 | 28.52 | 401.91 |

Type | $\mathbf{The}\mathbf{Equivalent}\mathbf{Maximum}\mathbf{Force}\mathbf{F}/\overline{\mathit{\rho}}$ (N) | $\mathbf{Equivalent}\mathbf{Strength}\mathsf{\sigma}$$/\overline{\mathit{\rho}}$ (MPa) | $\mathbf{Equivalent}\mathbf{Elastic}\mathbf{Modulus}\mathbf{E}/\overline{\mathit{\rho}}$ (MPa) |
---|---|---|---|

A2 | 2075.30 | 30.26 | 251.96 |

B2 | 2138.28 | 20.97 | 210.62 |

C2 | 2610.10 | 18.38 | 185.19 |

D2 | 2586.81 | 13.71 | 164.42 |

E2 | 2296.14 | 9.49 | 117.34 |

F2 | 1853.93 | 6.14 | 55.55 |

G2 | 2603.45 | 7.10 | 67.11 |

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## Share and Cite

**MDPI and ACS Style**

Zhang, D.; Tian, X.; Zhou, Y.; Wang, Q.; Yan, W.; Akmal Zia, A.; Wu, L.; Li, D.
Spatial 3D Printing of Continuous Fiber-Reinforced Composite Multilayer Truss Structures with Controllable Structural Performance. *Polymers* **2023**, *15*, 4333.
https://doi.org/10.3390/polym15214333

**AMA Style**

Zhang D, Tian X, Zhou Y, Wang Q, Yan W, Akmal Zia A, Wu L, Li D.
Spatial 3D Printing of Continuous Fiber-Reinforced Composite Multilayer Truss Structures with Controllable Structural Performance. *Polymers*. 2023; 15(21):4333.
https://doi.org/10.3390/polym15214333

**Chicago/Turabian Style**

Zhang, Daokang, Xiaoyong Tian, Yanli Zhou, Qingrui Wang, Wanquan Yan, Ali Akmal Zia, Lingling Wu, and Dichen Li.
2023. "Spatial 3D Printing of Continuous Fiber-Reinforced Composite Multilayer Truss Structures with Controllable Structural Performance" *Polymers* 15, no. 21: 4333.
https://doi.org/10.3390/polym15214333