Unmanned aerial vehicle, abbreviated as “Unmanned aerial vehicle” (UAV) refers to an aircraft that is operated either by radio‑controlled equipment and onboard programmable control systems, or by an onboard computer that enables fully autonomous or semi‑autonomous operation. As a new type of aerial platform, UAVs differ from manned aircraft in both operational requirements and mission objectives. Typically, UAVs are expected to meet criteria such as low cost, lightweight construction, high stealth, long endurance, and extended service life; for unmanned combat aircraft, additional demands include high maneuverability and substantial g‑loads.

Due to their high specific strength, high specific modulus, excellent designability, superior fatigue resistance, enhanced stealth performance, long service life, and good vibration‑damping properties, composite materials are widely used in most structural components of unmanned aerial vehicles, including the fuselage, wings, horizontal tail, vertical tail, tail boom, control surfaces, and landing gear.

The use of composite materials in UAV structures can reduce weight. 20%–30%. Currently, the industry regards the proportion of composite materials used as one of the key indicators for assessing the level of technological advancement of a UAV; typically, this figure should reach around 60%–80%. However, some U.S. UAVs have already achieved all-composite structures, with composite material content exceeding 90%.

Applications of Composite Structures in the Unmanned Aerial Vehicle Field

Polyacrylonitrile-based carbon fiber and Nomex honeycomb materials are widely used in drone airframes, wing skins, and leading edges. ； Foam‑core sandwich composites made from PAN‑based carbon fiber sheets and foam, or polyacrylonitrile‑based carbon fiber tubes, are extensively used as main spars in unmanned aerial vehicles; Kevlar fiber is employed in propellers, fuselages, and fasteners to significantly enhance fatigue resistance and impact performance. For medium‑ and large‑size UAVs, metallic materials are used for the primary load‑bearing structures, with composite materials for the remainder; small and medium‑size UAVs utilize carbon fiber, glass fiber, and their hybrid composites; unmanned combat aircraft employ carbon‑fiber composites and aramid fibers, among others. Small, low‑speed UAVs are constructed from carbon fiber, aramid fiber, paper honeycomb, and wood.

  Table 1 Specific strength and specific stiffness of materials used in unmanned aerial vehicles

     Because unmanned aerial vehicles (UAVs) do not need to account for human physiological limits in their structural design, they can focus more directly on optimizing maneuverability, leading to material selection that differs from that of manned aircraft. The use of composite materials can significantly enhance the airframe’s stealth performance. First, since polymers are electrically nonconductive, they help prevent the formation of scattering fields that would otherwise be detected by radar. Second, composites play a crucial role in achieving an effective integration of structure and function; for example, the application of structural‑integrated stealth materials can substantially reduce the airframe’s radar cross‑section. Finally, the use of composite materials enables an integral airframe structure, allowing for a smooth, monolithic design that achieves stealth by minimizing scattering of detection waves caused by discontinuities such as joints and fasteners. In summary, these design strategies effectively enhance the UAV’s concealment. According to statistics, countries worldwide now extensively employ advanced composites—primarily carbon‑fiber‑reinforced polymers—in UAVs, accounting for 60%–80% of the total structural mass and reducing the airframe weight by more than 25%. Initially confined to non‑load‑bearing components, carbon‑fiber composites are increasingly being adopted for load‑bearing structures as well. For instance, the Beijing Satellite Manufacturing Plant, in collaboration with the UAV Research Institute of the Ninth Academy of China Aerospace Science and Technology Corporation, successfully developed, using hand‑layup techniques, a composite bow‑shaped main landing gear and a carbon‑fiber composite tail boom for a specific UAV model. A summary of composite material applications in certain UAVs is presented in Table 2.

Table 2 Overview of Composite Material Applications in Unmanned Aerial Vehicles

Composite materials in reconnaissance /Structural Applications of Surveillance Drones

Using composite materials in reconnaissance and surveillance UAVs offers advantages such as high specific strength and specific stiffness, excellent fatigue resistance, superior vibration‑damping performance, and favorable manufacturability. Currently, both operational and development‑stage UAVs abroad predominantly employ hybrid structures combining composites with conventional aluminum alloys; for example, the U.S. “DarkStar” UAV features a composite airframe coated with radar‑absorbing material to meet its stringent stealth requirements. ； Israeli Many renowned unmanned aerial vehicles, such as the “Pioneer” and “Searcher,” the U.S. “Eagle Eye,” the British “Phoenix,” and South Africa’s “Vulture,” are all constructed entirely from composite materials.

At present, the world’s longest‑endurance and longest‑range unmanned reconnaissance aircraft belongs to the U.S. Air Force. The “Global Hawk” incorporates advanced composite materials for 65% of its overall structure. With the fuselage’s primary structure made of aluminum alloy, all other components—including the wings and tail surfaces—are constructed from graphite/epoxy composites. Parts such as the wings, tail surfaces, aft fuselage, radome, and engine nacelle utilize carbon fiber/epoxy composites. The Global Hawk unmanned combat aircraft employs autoclave‑based manufacturing techniques; wing fabrication primarily relies on a hydraulic autoclave process using Nomex honeycomb cores at 121°C. Wing spars and wing boxes are produced from high-modulus carbon‑fiber/epoxy prepregs supplied by Cytec, while the skin adopts a laminated sandwich construction. The inboard wing houses an integral fuel tank, and both leading and trailing edges feature honeycomb sandwich structures reinforced with Nomex cores provided by Hexcel. The main structural elements are cured in a 121°C autoclave, with spars and skins cured separately before being bonded together in a secondary step—eliminating fasteners and streamlining sealing and assembly processes. The entire wing is divided into three sections: a 15‑meter‑long wing box spanning the fuselage, two 10‑meter‑long outer wings, and wingtip assemblies. These sections are mechanically joined, with the surface coated in a lightning‑strike‑resistant mesh. For the RQ‑4B variant, the wingspan increases to 39.9 meters, with additional plies applied in certain areas to enhance structural strength and stiffness. The full wing is segmented into four parts: two large wing boxes mated at the fuselage center, and one wingtip assembly at each end. This mid‑fuselage junction of two composite structures improves aerodynamic efficiency. Notably, the wingtip assemblies are manufactured using Radius Engineering’s SQTM (Same‑Qualified Resin Transfer Molding) technology—a closed‑mold forming process that combines prepreg techniques with liquid‑molding methods, enabling the production of near‑net‑shape, highly integrated aerospace components. Although SQTM does not employ an autoclave, it can deliver parts comparable in quality to those produced in an autoclave, making it a cost‑effective manufacturing approach. The newly designed wingtips comprise three principal components: a torsion box, an inboard rib (connecting the tip to the main wing), and a wingtip cap. Each torsion box contains six laminated composite stringers, while the leading and trailing edges along with the outer wing ribs form a unified structure. Compared to the original design, which used two honeycomb‑core stringers and multiple wing ribs per torsion box, SQTM allows the complete fabrication of all left‑ and right‑wingtip components using just three molds.

United States The airframe of the RQ‑7 Shadow multirole UAV, developed by AAI, is composed of 95% composite materials: a carbon‑fiber‑reinforced epoxy composite fuselage, tail surfaces made of carbon‑ or aramid‑fiber‑reinforced epoxy composites, and wings constructed with a carbon‑fiber‑reinforced epoxy composite skin–honeycomb sandwich structure.

The “Suicide Bee” UAV from BAI Aviation Systems features wings, movable control surfaces, and a vertical tail all constructed from rigid shell‑type composite materials made of polystyrene and glass fiber. The rudder and fuselage employ a foam sandwich structure, while the engine cooling shroud and cabin door covers are produced via thermoplastic vacuum forming. The fiberglass propeller spinner is manufactured using compression molding. 。

No ·The renowned “Global Hawk” unmanned reconnaissance aircraft developed by Northrop Grumman has a wingspan of 35.4 meters, surpassing that of the Boeing 747. With the exception of the fuselage’s primary structure, which is made of aluminum alloy, all other components—including the wings, tail assembly, aft fuselage, radome, and engine nacelles—are constructed from composite materials, accounting for approximately 65% of the airframe’s total structural weight.

Germany’s Unmanned Aerial Systems Exploration Program The “Pike” unmanned technology demonstrator, manufactured in Augsburg using EADS’s patented vacuum-assisted manufacturing process, produced an all‑carbon‑fiber composite fuselage in just one month. Its all‑carbon‑fiber composite wings were fabricated in Getafe, Spain, and the aircraft’s only metal components are the wing spar, the main landing‑gear strut, and the mounting bracket.

China's The “Xianglong” unmanned reconnaissance aircraft features an ACM engine nacelle mounted at the rear of its fuselage; its streamlined, continuous contours provide excellent stealth performance. By contrast, the ASN‑105B unmanned reconnaissance aircraft is constructed primarily from fiberglass‑reinforced plastic, making it China’s first large‑size UAV to employ composite materials. The BZK‑05 long-range unmanned reconnaissance aircraft, jointly designed by Harbin Aircraft Industry Group and Beihang University, utilizes a conventional riveted aluminum alloy structure for its load‑bearing fuselage framework, while its skin and fairings are made of composite materials such as glass fiber, carbon fiber, and Nomex honeycomb. Its wings are also entirely composed of composite materials.

In addition, the Yilong UAV is a medium‑low altitude, dual‑use (military and civilian), long‑endurance multirole unmanned aerial vehicle developed by AVIC. Its airframe is constructed from aluminum alloy, its radome is made of wave‑transparent composite material, and its wings are honeycomb sandwich composites. Made in China. The Rainbow‑4 UAV has an 18‑m wingspan and a maximum takeoff weight exceeding 1,300 kg; with the exception of the main spar, all other structural components are made of composite materials. The Rainbow‑5 is equipped beneath its wings with… 6 A composite-material pylon capable of carrying multiple loads at once. 16 A variety of air-to-ground missiles, with a maximum payload of 1 Ton.

Structural Applications of Composite Materials in Reconnaissance-Strike Integrated UAVs

The composite materials used in the structure of unmanned combat aircraft are primarily carbon‑fiber composites, which significantly reduce the overall weight of the airframe, enabling the aircraft to achieve greater agility and higher speeds. Developed by Boeing, More than 90% of the X‑45 unmanned combat aircraft’s airframe is constructed from composite materials. Its fuselage is manufactured using low‑temperature‑cured prepregs, while its wings feature a foam‑sandwich structure that employs a proprietary FMC (Foam Matrix Core) technology: first, a foam core is molded; then, fibers are wound onto the cured foam; finally, the two components are co‑cured. This approach not only significantly reduces the X‑45’s manufacturing costs but also facilitates disassembly, storage, and installation.

Manufactured by Boeing of the United States The X‑45A unmanned combat aircraft has a wingspan of 10.3 m, a chord length of 8 m, and a mass of 3,640 kg. It can carry a payload of 680 kg, with composite materials accounting for 45% of the airframe’s structural mass. Its fuselage skin is fabricated from carbon‑fiber prepreg tapes laid up in a specific laminate sequence; the upper fuselage skin, approximately 9 m long and 3.7 m wide, is a single integral piece, while the lower fuselage skin consists of two sections, each measuring 4.5 m × 3.7 m. The upper and lower skins of the X‑45A’s exhaust nozzle are made from Cytec’s BMI‑5250‑4 carbon‑fiber prepreg, which cures at temperatures between 177°C and 204°C and operates within a service temperature range of −59°C to 204°C.

  Developed by the United States to secure its hegemonic position in the Western Pacific, The X‑47B unmanned combat aircraft can strike Chinese coastal missile units from beyond the range of China’s domestically developed anti-ship missiles. Its outboard wings are constructed from aluminum alloy components and carbon‑fiber epoxy composites, with 90% of the airframe surface made of carbon‑fiber composites; the wings feature a folding mechanism that helps conserve space aboard aircraft carriers. Israel’s “Sentry” unmanned combat aircraft can receive video, telemetry, and data broadcasts via an onboard surveillance platform and a mobile combat‑intelligence microwave data link. The entire airframe is fabricated from carbon‑fiber/epoxy composites, with an empty weight of up to 76 kilograms and a maximum payload of 118 kilograms. China’s “Lijian” is manufactured by Hongdu Aircraft Industry Corporation; it has a length of approximately 10 meters, a wingspan of 13.8 meters, and its structure is built using carbon‑fiber sandwiched between aluminum honeycomb cores.

A long-endurance, unmanned reconnaissance aircraft with a hollow fuselage, manufactured by General Atomics of the United States. The material distribution of the MQ‑1 “Predator” UAV reveals that, with the exception of the fuselage spar, nearly the entire airframe is constructed from composite materials, including carbon‑fiber, glass‑fiber, and aramid‑fiber composites, as well as honeycomb and foam sandwich structures. These composites account for approximately 92% of the structure’s total weight. Notably, the fuselage extensively employs carbon‑fiber fabric/Nomex honeycomb sandwich panels reinforced with stiffeners, while critical internal locations incorporate carbon‑fiber spars and ribs to ensure adequate stiffness. The radome is fabricated from glass‑fiber composites. In terms of manufacturing processes, the primary structural components are produced using manual layup of carbon‑fiber/epoxy prepregs followed by autoclave curing, whereas the main spar, tail‑plane spar, and landing‑gear struts are formed via closed‑mold molding with carbon‑fiber fabrics, aided by inflatable bladder consolidation.

Developed jointly by Tengdun Company and Sanqiang Company With the exception of the central fuselage frame, the HA unmanned reconnaissance and strike integrated platform is entirely constructed from carbon‑fiber and glass‑fiber composite materials. Figure 3 And the picture 4 They are respectively The HA UAV features a multi‑beam foam sandwich structure with an integrally cured vertical tail and a skid‑type landing gear.

                                            

Figure 3  HA UAV carbon fiber composite vertical tail

                                          

Figure 4  HA UAV carbon-fiber composite skid-type landing gear

Composite Materials in Structural Applications for Civil Unmanned Aerial Vehicles

Developed by the Polytechnic University of Turin in Italy The wing tubular beam structure of the HeliPlat high-altitude, long-endurance solar-powered UAV is fabricated using M55J carbon-fiber-reinforced epoxy composite panels with a Nomex honeycomb sandwich core, capable of withstanding most bending, torsional, and shear loads. The wing box skin is manufactured from M55J carbon fiber/epoxy prepreg tape.

Developed by Aurora Flight Sciences The “Theseus” high-altitude, long-endurance atmospheric research UAV is primarily used for studying atmospheric convection, remote sensing, and hurricane detection. The aircraft features an all-composite structure, with a high-wing span of 42.06 m; during transport, the outboard wing sections and tail can be detached. The all-composite wing spar of the HALE-UAV demonstrator is shown in the figure. 5  As shown.

                                                 

Figure 5  All-composite wing spar of the HALE-UAV demonstrator aircraft

United States NASA’s Helios solar‑powered, all‑composite civil unmanned aerial vehicle achieved a continuous flight duration of 17 hours during its 2001 test flight, setting a record for the longest sustained flight by an unmanned aircraft. As shown in the figure. 6 As shown, the wingspan of this aircraft is With a wingspan of 75.3 meters—far exceeding that of the Boeing 747—the aircraft features a 2.44-meter chord and a primary structure made of carbon fiber/epoxy composites. The entire airframe is evenly divided into six sections, each equipped with a composite payload bay at its junction to accommodate payloads.

                                 

Figure 6  United States NASA’s “Helios” solar-powered all-composite-material unmanned aerial vehicle

Recently, the China Aviation Industry Corporation’s First Aircraft Design Institute successfully completed final assembly of its independently developed ultra-long-endurance solar-powered unmanned aerial vehicle, which has been named… “Morning Star,” as shown in the figure. 7 As shown, the entire airframe is constructed from carbon‑fiber composite materials. Civil‑use unmanned aerial vehicles (UAVs) predominantly employ vacuum‑bag molding, which helps reduce manufacturing costs. This process is easy to operate and does not demand particularly stringent technical specifications.

                                                               

Figure 7  China Aviation Research Institute “Qimingxing” Solar-Powered All-Composite Civil Unmanned Aerial Vehicle

Design of Co-cured Composite Structures for Unmanned Aerial Vehicles

To achieve better weight reduction, increase payload capacity, and extend endurance, lightweight composite‑material design has become the prevailing trend in modern UAV development, with this trend centered on integrated structural design and manufacturing.

As the use of composite materials increases, structural complexity continues to rise. It becomes highly valuable to fully exploit the potential of composites, significantly reduce weight, further simplify assembly by adopting integrated structures, and streamline manufacturing processes. In UAVs, structures are typically fabricated separately as panels, beams, and ribs, then assembled via room‑temperature adhesive bonding: first, single‑sided panel components are bonded to the skeleton, followed by bonding with another panel; however, bond quality cannot be monitored. This project aims to explore and establish a one‑step co‑curing process for bonding wall panels to beams. (Medium-temperature curing) delivers higher bond strength and greater reliability, shortens component assembly cycles, significantly reduces costs, and minimizes the use of fasteners.

Co-curing design and manufacturing technologies are highly advanced, enabling the full exploitation of composite materials’ advantages—such as high designability, superior specific strength, and high specific modulus—while facilitating further lightweighting. This approach helps achieve system weight reduction, increased mission payload, and extended endurance.

The application areas of composite materials have expanded from non-load-bearing and secondary load-bearing components to primary load-bearing structures. The development trend is moving toward larger sizes, monolithic integration, and reduced costs. Composite integral molding technologies achieve lightweight, high‑performance, and low‑cost components by minimizing the number of parts and fasteners required in complex, large‑scale assemblies. Among these technologies, co‑curing stands out as the preferred approach, yielding composite parts with light weight and minimal deformation.

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