Samantha Scudder, Product Manager Tubes & Defense, Exel Composites, explores how composite materials can be engineered around different drone demands
A delivery drone carrying parcels through a city, a surveillance unmanned aerial vehicle (UAV) mapping a construction site and a defense drone maintaining communications in the field may all look broadly similar, but their design requirements can be very different.
There is no single recipe for effective drone structure. A logistics drone must maximize payload without compromising flight range, while a surveying platform needs to keep cameras and sensors stable enough to capture accurate data. An inspection UAV may have to operate in rain, salt-laden air or difficult industrial environments, and specialist surveillance equipment can introduce additional requirements such as radio-frequency transparency.
Drone applications share common design requirements too. No matter their intended use, increasing pressure on the airframe will be on any manufacturer's mind – particularly as drone technology becomes more and more advanced. But it's not simply a lightweighting question. Every gram devoted to structure cannot be allocated to batteries, sensors or payload but, in parallel, reducing mass cannot come at the expense of rigidity and durability.
This is where the structural efficiency of composites becomes particularly valuable.
Putting fibers where they matter
One of the major advantages of composites is the number of design variables available to the engineer. Rather than simply selecting a material and then determining the dimensions of a component, designers can adjust reinforcement type, fiber orientation, profile geometry, tube diameter and wall thickness together to achieve the required mechanical behavior. At Exel Composites, engineers can select and combine these variables around the specific load cases, weight targets, and functional requirements of the finished component.
Higher specific stiffness can minimize structural deflection without introducing unnecessary mass. Tube diameter and wall thickness can be optimized around a particular stiffness-to-weight target, while the geometry of the profile itself can be designed to resist bending and other stresses.
This is particularly useful in UAV structures, where load cases can vary substantially between components. An airframe boom, for example, may need to withstand the combined forces generated by motors, propellers, payloads or tail assemblies while maintaining low weight and high stiffness. Other structural elements, such as wing members or lattice mast systems, will experience different combinations of bending, torsional and vibration loads. Exel can therefore tailor each profile with a specific geometry and fiber architecture to deliver the required performance.
A tailored fiber architecture also creates efficient load paths through the component, allowing forces to be transferred more effectively along the structure. Longitudinal fibers can provide stiffness along the main axis, while fibers introduced at different angles can improve resistance to torsional and transverse loading. This allows engineers to tailor the fiber architecture to the direction and type of loads the component is expected to experience.
Hybrid fiber designs extend this further. Different reinforcement types can be combined to balance strength, stiffness and impact resistance, while also introducing application-specific properties. For example, carbon fiber composites provide excellent stiffness-to-weight performance but their electrical conductivity can make them unsuitable around sensitive communication systems. Glass fiber reinforcement can instead provide RF transparency where signals must pass through the structure.
Benefitting from continuous processes
Achieving the required qualities drone manufacturers expect is only part of the challenge. Developers may move quickly from prototype to considerably larger production volumes, making the ability to produce continuously just as important.
Continuous manufacturing processes, such as pultrusion and pull-winding, offer enormous advantages here. Pull-winding is particularly important when producing thin-walled UAV structures and something that Exel has decades of experience in applying. During the process, longitudinal fibers are combined with helically wound fibers placed at controlled angles within the composite. This creates a tailored reinforcement architecture, with longitudinal fibers providing high axial stiffness and efficient load transfer along the length of the profile, while angled fibers improve resistance to torsional, transverse, and multi-axial loading.
By adjusting factors such as winding angle, fiber volume, reinforcement type, and resin formulation, engineers can tailor the stiffness and strength of a profile to meet specific loading conditions without simply increasing wall thickness and structural mass.
The same continuous process can then reproduce that architecture across large quantities of profiles with high consistency and low product-to-product variability. Minimal post-processing can also reduce the number of manufacturing operations required once UAV production moves to higher volumes.
As UAVs take on longer missions and greater payloads, the challenge for structural engineers will increasingly be about extracting more performance from the same mass. This demands more than simply selecting a lightweight material. Engineers must manage stiffness, fatigue, environmental exposure, impact requirements, and complex loading while also considering how the aircraft will eventually be manufactured at scale.
Composite structures provide a way to address these requirements together. For airframes, wing structures, lattice masts and VTOL platforms alike, the opportunity is therefore not simply to make the structure lighter – it's to design the structure more efficiently around what the UAV actually needs to do.
Are you designing drones that must deliver consistent performance? Read Exel Composites' case study on their work with ANT-X to see how continuously produced composite tubes solved quality and variability issues at scale for the drone manufacturer.
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