综述：用于航空航天领域的聚合物和复合材料的增材制造

《Materials Horizons》：Additive manufacturing of polymers and composites for applications in aerospace and aeronautics

增材制造（AM）通过减少部件组装和人工干预，推动航空航天生产方式的革新，实现复杂几何结构制造和材料节约，并逐步向太空在轨制造（如回收利用和本地资源利用）发展以降低地球补给需求。

　　
### Analysis of Additive Manufacturing (AM) in Aerospace and Aeronautical Applications

#### **Introduction**
Additive manufacturing (AM) has revolutionized aerospace and aeronautical industries by enabling the production of complex, lightweight, and customized components. Traditional subtractive methods are limited by high material waste, long lead times, and the inability to create intricate geometries. AM technologies, such as fused filament fabrication (FFF), direct ink writing (DIW), stereolithography (SLA), materials jetting (MJ), and selective laser sintering (SLS), offer solutions by minimizing part count, reducing costs, and enhancing design flexibility. Key applications include lightweight structures, sensors, and components for satellites and aircraft.

#### **Key AM Technologies in Aerospace**
1. **Fused Filament Fication (FFF)**
- **Process**: Layer-by-layer deposition of thermoplastic filaments melted by a heated nozzle.
- **Materials**: ABS, PLA, PEEK, PEI, and composites with fibers (e.g., carbon fiber-reinforced ABS).
- **Advantages**: Low cost, high material versatility, scalability, and suitability for large components.
- **Applications**:
- NASA’s In-Space Manufacturing Experiment (IMX) printed ABS components in microgravity.
- Airbus used FFF to print a 15% lighter bracket for the A320, reducing assembly time.
- Rapid prototyping of aerospace interiors (e.g., class dividers, seat panels).
- **Limitations**:
- High temperature requirements for certain materials limit use in extreme conditions.
- Warping and shrinkage due to cooling rates.
- Limited resolution for intricate geometries.

2. **Direct Ink Writing (DIW)**
- **Process**: Jetting viscous polymers or resins onto a substrate, often with UV or laser curing.
- **Materials**: Thermosets (e.g., UV-curable resins), elastomers, and conductive inks (e.g., carbon nanotubes).
- **Advantages**: High precision (10–500 μm), multi-material printing, and flexibility for complex shapes.
- **Applications**:
- NASA’s KArLE system for geochronology used SLA and DIW for micro-components.
- piezoelectric sensors for structural health monitoring (SHM) in satellites.
- Soft robotics for maintenance in space habitats.
- **Limitations**:
- High cost and limited industrial adoption due to low flow rates and material constraints.
- Challenges in integrating nanoparticles without affecting printability.

3. **Stereolithography (SLA)**
- **Process**: UV curing a liquid resin layer-by-layer using a laser.
- **Materials**: Photopolymers (e.g., UV-curable acrylates, epoxy-based resins).
- **Advantages**: Smooth surface finish, high resolution (20–100 μm), and suitability for functional components.
- **Applications**:
- NASA’s KArLE optical system with laser-cured resins.
- High-precision sensors and antennas for UAVs.
- Medical devices and flexible electronics.
- **Limitations**:
- Limited to UV-curable materials.
- High energy consumption and cost.
- Shrinkage and warping in large parts.

4. **Materials Jetting (MJ)**
- **Process**: Simultaneous jetting of multiple materials (e.g., thermoplastics, conductive polymers) using UV curing.
- **Materials**: Digital ABS, Tango Plus, PEEK, and hybrid composites.
- **Advantages**: Multi-material integration, high resolution, and surface quality.
- **Applications**:
- Functional coatings for thermal protection in satellites.
- Complex geometries in aircraft interiors (e.g., 3D-printed molds for thermoforming).
- Flexible electronics for UAVs.
- **Limitations**:
- High cost and limited to commercial thermoplastics.
- difficult to scale for large components.

5. **Selective Laser Sintering (SLS)**
- **Process**: Laser melting of polymer powder layers, no supports needed.
- **Materials**: PA12, PEEK, TPU, and composites with fibers or nanoparticles.
- **Advantages**: No support structures, high strength, and thermal stability.
- **Applications**:
- Boeing’s Alice V2 winglet printed with PA12.
- Carbon fiber-reinforced parts for structural components.
- Recyclable materials (e.g., thermosets) for sustainable manufacturing.
- **Limitations**:
- High material costs and complex powder handling.
- Limited to thermoplastic and thermosetting polymers.

#### **Material Selection and Challenges**
- **Polymer Matrixes**:
- **Thermoplastics**: Dominant in FFF and SLS (e.g., ABS, PA12) due to recyclability and processability.
- **Thermosets**: Used in SLA and DIW for high thermal stability (e.g., epoxy resins).
- **Elastomers**: Critical for vibration damping and flexibility (e.g., TPU, silicones).
- **Nanocomposites**:
- Carbon nanotubes (CNTs) and graphene enhance electrical conductivity and mechanical properties.
- Challenges include filler dispersion and interfacial bonding.

- **Smart Materials**:
- **Electro-thermal heating**: Used in de-icing systems for aircraft.
- **Piezoresistive/Piezolectric Sensors**: For structural health monitoring in satellites.
- **Self-healing Polymers**: Emerging for reducing maintenance costs in aerospace components.

#### **Case Studies and Industrial Applications**
- **NASA’s In-Space Manufacturing**:
- FFF printed ABS components in microgravity, demonstrating feasibility for on-demand repairs.
- KArLE system for lunar sample analysis, combining SLA and CVD for micro-scale parts.
- **Boeing and Airbus**:
- FFF-printed lightweight brackets reducing part count by 40%.
- MJ-printed components for UAVs and 3D-printed tooling.
- **CubeSat Manufacturing**:
- SLS and FFF used for complex satellite structures (e.g., Antennas, solar panels).
- Reducing launch costs by minimizing part count and weight.

#### **Challenges and Future Directions**
- **Material Limitations**:
- High-performance thermoplastics lack the strength and thermal resistance of metals.
- Nanocomposites face dispersion challenges in AM processes.
- **Process Optimization**:
- Integrating AI/ML for real-time parameter adjustment (e.g., detecting defects during printing).
- Developing in-situ curing techniques for space applications.
- **Sustainability**:
- Recyclable thermosets and bio-based materials (e.g., PLA from agricultural waste).
- Reducing energy consumption in powder handling and curing.
- **Scalability**:
- enlarging build volumes for structural components (e.g., aircraft wings).
- hybrid AM systems combining FFF, SLS, and MJ for multifunctional parts.

#### **Conclusion**
AM is transformative in aerospace, offering lightweight, customizable, and cost-effective solutions. While FFF dominates for large components, SLA and MJ excel in precision and multi-material integration. Challenges like material limitations, high costs, and scalability remain. Future advancements will focus on smart materials, AI-driven process optimization, and sustainable practices, enabling broader adoption in space missions and aeronautical engineering. Collaboration between industries and research institutions is critical to overcome technical barriers and realize the full potential of AM in aerospace.