无人机机体结构件用什么尼龙?次承力件才是它真正的主场

应用领域 发布时间: 2026-09-16 2209 阅读

What type of modified nylon is used for the airframe parts of the 108 drone?

Hierarchical material selection for aircraft structure

The drone body is not a single material. The main load-bearing components (arms, central plate) use carbon fiber epoxy composite or carbon fiber reinforced PA.

Secondary load-bearing components (motor mount, gimbal bracket, landing gear) use PA66-GF30 up to GF50;

Functional components (antenna cover, battery compartment, wire clip) use PA66-GF20 or PA12.

Modified nylon in drones serves as secondary load-bearing and functional components, while the primary load-bearing is the composite structure.

On-site restoration

Last spring, at a shipowner complaint handling meeting at a ship equipment factory, the engineering manager spread out a photo of the piping system. On a cargo ship along the coastal route, there was leakage at the joints of the ballast water pipes, and rust had flowed more than a meter along the hull. The shipowner's exact words were: 'My ship runs the Middle East route, with a hold temperature of forty degrees. What temperature were your pipes designed for?'

Conventionally designed, that's correct, but the cabin temperature in the Middle East broke through the conventional design. Later, the materials at the joints were upgraded overall, and the leakage repairs were completed within three months. From then on, this factory put the climate of the flight routes on the first page of the quotation, and material specifications followed the flight routes; this was the understanding they gained through repairs.

Core requirements of the boom and motor base

The boom bears the motor thrust, propeller vibration, and landing impact, making it a fatigue part. The core indicators are fatigue strength and creep resistance, not static tensile strength.

PA66-GF40 is mainstream in this position — GF40 has 25% higher stiffness than GF30 and 30% better toughness than GF50, making it a compromise between stiffness and toughness.

The motor mount needs to additionally consider motor heating—the motor mount temperature can reach 80-100°C, and a heat-resistant stabilizer should be added.

Vibration fatigue is a hidden killer

The drone's propeller rotates at high speed, and the body is subjected to high-frequency vibration for a long time. The fatigue strength of PA is only 25%-30% of its static strength, far lower than that of metal.

Three things to do in the design: first, add ribs at vibration node positions; second, avoid sharp corners and sudden thickness changes; third, use metal inserts at critical joints to distribute stress.

Many structural fractures are not due to insufficient strength, but fatigue cracks originate from sharp corners.

The boundary between weather resistance and moisture absorption

Drones mostly operate outdoors, and PA66 experiences a 30%-40% decrease in stiffness after absorbing moisture — this is a hidden cause of many flight accidents.

In areas with high humidity, three points should be considered: first, use PA66-GF40 instead of GF30, leaving a margin for stiffness after moisture absorption;

Second, perform surface pore sealing treatment; third, long-term storage should be dry.

PA12 with lower water absorption is suitable for making thin-walled functional parts, but it is expensive.

Lightweighting needs to consider the entire machine

Drone weight reduction directly translates to longer flight time, and every 1 g matters. But when it comes to modified nylon, weight reduction has to be considered for the whole machine: GF50 is only 0.07 g/cm³ denser than GF30, yet its stiffness is 35% higher—

On parts with limited stiffness, adding fiber actually reduces weight (allowing for thinner walls).

What really needs to be reduced is density: the density of the mineral-filled system is lower, making it suitable for non-load-bearing cover plate components.

Extended Judgment: Hidden Variables of UAV Structural Components

There are three hidden variables that are easiest to overlook. The first is the anisotropy caused by glass fiber orientation — the shrinkage difference between the flow direction and the perpendicular direction of injection-molded parts is 0.3%-0.5%, slender machine arms will warp, and mold flow analysis needs to be performed on the mold.

Second, recycled material is strictly prohibited — adding recycled material to fatigue parts reduces lifespan by more than 50%. Third, low-temperature high-altitude environments — at altitudes where the temperature is below -30℃, the glass transition temperature of the toughening agent must be lower than the operating temperature, otherwise the toughening will fail.

A deeper look: The origin of several numbers

Among the four operating conditions of ship pipelines, the ballast water system is the most corrosive. The combination of seawater, microorganisms, and treatment chemicals continuously chemically attacks the materials.

Long-chain nylon has good chemical resistance, but chloride ions in seawater have a targeted attack on certain systems. Chlorine resistance testing cannot be skipped. The difference between soaking in lab saltwater and real seawater lies in the microbial aspect. If conditions allow, it is recommended to do an actual seawater exposure test as a supplementary round.

Long carbon chain nylon is the main material for marine pipelines. Its low water absorption provides dimensional stability, and the seals at the joints are not affected by humidity changes. Long carbon chains also have good low-temperature toughness; during winter operations at northern ports with temperatures below minus ten degrees, the pipeline's resistance to freeze-thaw expansion is an inherent performance.

The material price is somewhat higher, but the cost of pipeline leaks is amplified tenfold on the ship. Maintenance depends on the available dock repair window, and the cost of one dock repair is enough to replace all the pipelines on the ship.

Hydrolysis resistance is a key indicator for water pipes. In high-humidity environments near hot water pipe sections and ballast tanks, hydrolysis of ordinary nylon is a chronic issue, leading to embrittlement and cracking after several years.

The selection of hydrolysis-resistant grades is classified according to the location of the pipe segment. High grades are used near the heat source and in areas that are constantly wet, while the rest are selected according to the standard. The cost saved by graded material selection can cover the price difference of upgrading all the materials on the ship, and it is worth calculating this for the shipowner.

Water hammer resistance and freeze-thaw resistance are structural-level considerations. The impact pressure from water hammer is several times that of static pressure, and the rigidity design of pipe clamps determines the force path of the piping. The clamp spacing for plastic pipes needs to be denser than for metal pipes. Freeze-thaw issues are a concern for northern ships; residual water inside the pipes can freeze and expand. The lowest points and elbows of the piping are high-risk locations for freeze-thaw cracking, so both drainage design and low-temperature toughness of the materials act as double insurance.

Fuel lines must pass through both electrostatic and permeation checks. The accumulation of static electricity on plastic pipes is a safety hazard, so conductive-grade pipes combined with grounding design are used. Permeation refers to the low-molecular components of fuel passing through the pipe wall, and if the permeation rate exceeds the standard, the cabin will be full of a fuel smell. There are dedicated methods for verifying both checks, and the materials used for fuel lines are among the most rigorously tested types in marine plastics.

The cabin temperature is the baseline for material selection. The cabin temperature is usually 40 to 50 degrees Celsius throughout the year, and it can reach 60 degrees on routes in the Middle East and near the equator. The temperature rating of pipelines is determined by adding the maximum cabin temperature to the temperature of the medium inside the pipeline. If the temperature rating is set too low, the overall lifespan curve shifts downward; if set too high, the cost increases. Determining values by region is the direction of refined design. Pipelines on the same ship can be divided into two levels according to the region.

Engineering Test: 4 Mandatory Tests

Test 1: Fatigue strength. PA66-GF40 has a fatigue strength of 28% of its static strength at 10⁷ cycles, while carbon fiber composites are 55% — fatigue is the weak point of PA.

Test 2: Stiffness after moisture absorption. After PA66-GF30 absorbs 2.5% moisture, the flexural modulus decreases by 38%, and GF40 decreases by 32% — extra margin should be left in the wet area.

Test 3: Comparison of GF content. The flexural modulus of GF30/GF40/GF50 is 8500/10500/13000 MPa respectively, and the notched impact decreases in order 12/9/6.5 kJ/m².

Test 4: Weight reduction account. The robotic arm is changed from PA66-GF30 to GF40, wall thickness is reduced by 0.4 mm, single piece weight is reduced by 8 g, stiffness remains the same.

Boundary Declaration

Operating conditionRecommended materials
Boom / Central PlateCarbon fiber composite material or carbon fiber reinforced PA
Motor Mount / Gimbal BracketPA66-GF40 Heat Resistant
Landing gearToughened PA66-GF30
Antenna Cover / Battery CompartmentPA66-GF20
High humidity areaPA66-GF40 or PA12

Engineering Memo

The main load-bearing structure of the drone is made of composite material, while modified nylon is used for secondary load-bearing and functional parts — GF40 is a compromise between stiffness and toughness.

The real shortcomings are fatigue (only 28% of static strength) and a 38% decrease in stiffness after moisture absorption; these two points must have a margin.

Three consecutive follow-up questions

Question 1: How much metal piping can plastic piping replace on a ship? In the lower section of the seawater system with large diameters, metal still dominates, while plastic pipes can replace upper sections and small diameters to a higher extent. The boundary for replacement is determined by fire protection and mechanical damage risks, which are also limited by regulations. The boundaries are set according to the allowable range of classification societies, and replacement is allowed within the regulations.

Question 2: What method is used for pipeline connections? Mainly butt fusion and flange connections are used. The reliability of butt fusion depends on process parameters, while flange connections have good removability. Since maintenance conditions on the ship are poor, enough space should be left for flange positions, and butt fusion should be done correctly the first time. The distribution of the two methods is designed according to the maintenance plan, and the maintenance plan is part of the pipeline design.

Question 3: Is classification society certification troublesome? The certification cycle for materials is counted in years, but once certified, it becomes a long-term qualification. Certificates from classification societies are the passport for marine materials. The testing items for certification largely overlap with routine verification. If the overlapping items are completed in advance all at once, the incremental cost of certification is controllable. This investment is a must for manufacturers making marine products.

Reverse Cases and Final Judgments

A certain factory equipped a river ship with marine-spec pipelines. The material grade was over-specified, which increased costs; the shipowner accepted this. However, after delivery, the feedback from the engine room installation was that the pipes were too stiff, and the scrap rate in the bending process increased. Marine materials are stiff, and river ships have small-diameter pipes with many elbows, making workability a new problem.

The lesson from this case is that higher material grades are not necessarily better; specifications should follow the working conditions. The money spent on over-specification is spent on unnecessary indicators, while the scrap rate of elbows is the real cost. The rationality of selection lies in matching, not in stacking higher.

Practical Case Study: Common Pitfalls and Correct Solutions

Pitfall 1: Directly applying the physical property table of ordinary industrial parts to special aviation scenarios, resulting in smoke and toxicity exceeding standards / low-temperature brittleness / failing flame-retardant reinspection after half a year of installation.

Correct: For this type of scenario, standard prerequisites apply — all the flammability and smoke toxicity standards for airworthiness or rail transit, as well as low-temperature impact standards, need to be re-checked. The property tables for regular modified nylon only cover ambient temperature mechanical properties and are completely unsuitable — this is the root cause of 80% of the initial sample failures.

Pitfall 2: To reduce weight, the fiberglass content was increased all the way, resulting in exposed fiberglass in thin-walled areas, surface fiber bloom, and dimensional deviations. Correct approach: Weight reduction should rely on structure rather than simply adding fibers. For thin-walled parts, stick to a GF30 limit; if exceeded, switch to a high-flow grade or add mineral fillers.

Pitfall 3: Only verifying performance at room temperature, neglecting alternating high and low temperatures and salt spray. Correct approach: Service environment verification should be based on the entire machine's lifespan, with high and low temperature cycling, salt spray, and damp heat aging carried out together; missing any one of these is a hidden risk for mass production.

These three pitfalls are all checklists that must be self-inspected before mass production.

Supplementary note: Four extensions from ship piping judgments

The proof of the service life of marine pipelines is shifting from random inspections to condition monitoring. Key pipeline sections are equipped with strain and temperature sensors, and life predictions are supported by data. The accumulation of monitoring data makes the material life curves more accurate and provides material suppliers and shipowners with a data-based language for direct communication. The digitization of pipelines is a new opportunity for material suppliers, and the ability to interpret sensor data is a new service product.

Under the trend of green ships, the environmental requirements for materials used in ballast water and emission systems are increasing, and environmental declarations and recyclability of materials have entered the shipowner's list of concerns.

The contribution of lightweight plastic piping to ship fuel consumption can be quantified. The fuel saved per kilogram over the voyage can be calculated, and if this calculation is shown to the ship owner, the story of plastic piping becomes convincing. Here, environmental protection and saving money are the same thing.

The ship repair market has a fast-response demand for piping components. The window for ships to dock is short, so the supply of piping components needs to be measured by the hour. The stocking structure for ship repair parts differs from regular supply; the inventory depth of commonly used specifications is the core of competitiveness. Inventory turnover and fast-response capability have made the ship repair market a rare retail-type business in the manufacturing industry, requiring material suppliers to change their approach in this area.

The evolution of standards for marine plastic piping is worth paying attention to. The range of systems allowed is expanding, and each revision of the standards opens up new alternative options. By keeping track of the pace of standard revisions and preparing material solutions for newly allowed systems in advance, you will be the most ready supplier when the standards come into effect. The first-mover advantage in compliance windows is particularly evident in the marine market.

Supplement: Four more observations from the cabin

Observation one: The inspection data of the cabin pipelines can be used to optimize the design. The failure records of the ship's pipelines are classified by location and pattern, and the locations with a high incidence of failures indicate the weak points in the design.

A factory organized the fault records of dozens of ships into a design improvement list. For the next batch of ships, the piping layout was directly revised on the drawings, reducing the failure rate by half. Organizing after-sales data is a one-time investment, and the benefits extend across the entire product generation.

Observation two: The crew's operating habits are part of the pipeline conditions. The speed at which valves are opened and closed, as well as the techniques used during disassembly and assembly for maintenance, can change the stress on the pipeline. Provide the crew with a page of illustrated instructions for operation, clearly showing the key points for valve speed and disassembly/assembly of plastic pipelines. Faults caused by operation can be reduced by 30%. The enemy of materials is often not the environment, but the way they are used.

Observation three: The market for ship modification and repair has a scattered demand for piping components but good profit margins. Modification orders are quoted per project, selling materials together with processing. The material plan for a modification project needs to match the temporary inspection of the classification society, and the speed of document preparation determines the ability to secure orders. Competition in the modification market is both about speed and documentation.

Observation Four: The electrification of inland vessels brings new piping requirements. The cooling piping for battery compartments and fire protection piping are newly added systems, and the operating conditions of these systems are different from those of traditional piping.

Piping components for electric boats are a new growth point in the marine market. The chemical resistance of coolants and the tolerance of fire-fighting media are two new challenges. Manufacturers that first establish a verification plan get the orders. No one is currently in place for the new systems, so everyone is starting from the same starting line.

Conclusion

Make your point clear first, then talk about the price—when it comes to choosing materials, the earlier you ask, the easier it is.

The material selection and mold trial for this type of part can be discussed together.

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