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Legal Notice: All DUC propellers have a maximum lifetime limited to 600h on direct drive engines (i.e Jabiru, UL Power, Continental, Volkswagen, Limbach) and 800h on Rotax and HKS engines. Structural guarantee is 6 months from date of payment. Average lead time is 2 months from date of payment.
Safety warning-Jabiru engines: Following an accident, the company DUC Helices has sent an email to inform...Read the message Contents of this page1°) Design 2°) Technology 3°) Testing 3.1) Testing of Blades 3.1.1) Type of engine 3.1.2) Calculation of the centrifugal force 3.1.3) Static Pulling 3.2) Testing of hubs 3.2.1) Between Forged carbon process and autoclave process 3.2.1.1) Draping 3.2.1.2) Results 3.2.1.3) Conclusion 3.2.2) Between Forged carbon and forged aluminium 3.2.2.1) Materials and parts 3.2.2.2) Testing procedure 3.2.2.3) Results 3.2.2.4) Conclusion DesignComputer Aided Design Computer-Aided Design (CAD) is the use of computer technology to aid in the design and particularly the drafting (technical drawing and engineering drawing) of a part or product, including entire buildings. It is both a visual (or drawing) and symbol-based method of communication whose conventions are particular to a specific technical field. Drafting can be done in two dimensions ("2D") and three dimensions ("3D"). Drafting is the communication of technical or engineering drawings and is the industrial arts sub-discipline that underlies all involved technical endeavors. In representing complex, three-dimensional objects in two-dimensional drawings, these objects have traditionally been represented by three projected views at right angles. Computer-Aided Design is one part of the whole Digital Product Development (DPD) activity within the Product Lifecycle Management (PLM) process, and as such is used together with other tools, which are either integrated modules or stand-alone products, such as Computer-aided manufacturing (CAM) including instructions to Computer Numerical Control (CNC) machines  Design and implementation of DUC propellers is done using Thinkdesign "Think3" CAD design software enabling DUC Propellers to incorporate the ultimate optimisation of the blade’s geometric definition.  As a result, DUC propeller design is always based on a extensive calculations including:
Back to TOP Forge carbon ProcessDuc propellers is a division of Carbon Forgé SAS. Carbone Forgé SAS company designs, develops and transforms composite parts made of long carbon fibres and thermoset or thermoplastic resin. Thanks to exclusive patented processes, Carbone Forgé SAS is able to produce specific parts with mechanical vocation, with levels of precision and complexity never reached so far in the composites universe. Process AdvantagesTechnical:
Economic:
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Applications USA - Composites Atlantic  France - Bicycle   Swiss - Luxury wristwatch  Swiss - Medical Back to TOP TechnologyClick to enlarge DUC propellers are manufactured entirely out of composite materials. The blades are made of layers of pre-impregnated, high-resistance carbon fibre. Polymerisation is performed in a press at a pressure of 6 bars, with a Rohacell core. An inconel leading edge can be inserted during the manufacturing process. RohacellROHACELL® is a close cell polymethacrylimide- (PMI-) rigid foam, that is used as a core material for sandwich constructions. It shows outstanding mechanical and thermal properties. In comparison to all other foams it offers the best ratio of weight and mechanical properties as well as highest heat distortion temperature. Rohacell is 5 folds more expensive than other core foam like Armacell, but its characteristics are offering tremendous advantages for propeller manufacturing. Compare to other foam behaviour, Rohacell is a dynamic material: when used under high temperature and high pressure autoclave and resin infusion processes, Rohacell doesn't stay compressed and keep expanding therefor increasing sticking between core and prepreg. After manufacturing, Rohacell will dynamically contribute to the rigidity of the blade especially in torsion whereas static foam will mostly contribute to the profile. Lightweight Construction for AircraftThe classical requirement to be met in aircraft design is low weight combined with optimum mechanical properties. ROHACELL® is widely used as core material for demanding sandwich structures ROHACELL® shows outstanding strength - to - weight ratio even at elevated temperatures and excellent fatigue behavior. Due to the good resistance to compressive creep, it can be used under high temperature and high pressure autoclave and resin infusion processes. Rotor Blades for Helicopters ROHACELL® has become an integral part in a whole range of helicopter rotor blades made by a wide variety of manufactures. Using Röhm's in-mold pressing technology for the EH 101, GKN Westland produces the biggest helicopter rotor blade to date, which is approximately 8 meters in length. The durability of the main and tail rotor blade with ROHACELL® is guaranteed for the lifetime of the helicopter.  Main and tail rotor blade of Eurocopter EC 135 with ROHACELL®. ProcessingROHACELL® can be cut, sawn, drilled and NC machined by means of high-speed woodworking or plastic processing machines, without the use of a lubricant. It can also be thermoformed to even complex shapes. All reaction adhesives systems are suitable for bonding ROHACELL® IG to itself or to other materials. It is compatible with any adhesive systems and resin, and can also be combined with thermoset and thermoplastic prepregs without any problems. Structural components can be manufactured both in the autoclave or resin infusion (RTM, DPRTM, VARTM, SCRIMP). and by wet hand lay-up. The particular advantage of ROHACELL® is that it offers the possibility of cocuring sandwich components in just one process step integrating the cure of the skins and the bonding of the skins to the core. Download the Data Sheet of Rohacell for Aviation Back to TOP PrepregsStructilAknowledged by QUALIFAS since 1995, STRUCTIL is present on the Aerospace market as a provider of resins, structural adhesives, prepregs and pultruded profiles:
The STRUCTIL Research and Development, Control, Production and Sales departments, acting under the control of its ISO 9001 certified Quality Assurance system, are organized to satisfy the requirements of the Aerospace industry. HexcelHexcel is a leading worldwide supplier of composite materials to aerospace and other demanding industries. Hexcel today offers a breadth and depth of products and services that is unmatched in the industry. From its worldwide manufacturing facilities Hexcel manufactures the full spectrum of advanced material solutions- this includes everything from carbon fiber and reinforcement fabrics to pre-impregnated materials (or "prepregs") and honeycomb core, tooling materials and finished aircraft structures. Hexcel consumes a portion of its own fiber, fabric and composite material production internally, with the balance sold into the various markets in which it competes. Thus ensuring that the entire product line is exposed to market forces spurring innovation and cost-competitive production. As the most vertically integrated supplier in the industry, Hexcel is better able to control the cost, quality and delivery of its products. Vertical integration also means that Hexcel can offer enhanced design flexibility and support to customers worldwide. Hexcel's research and technology function supports its businesses worldwide with a highly developed expertise in materials science, textiles, process engineering and polymer chemistry. R&T also performs contract research for customers in the US and Europe. Worldwide investment in R&T is coordinated by a committee of managers from each of Hexcel's businesses. Download the Data Sheet for M52 HexPly 120°C Download the Data Sheet for M96F HexPly 160°C Back to TOP InconelInconel is refractory stainless superalloy with the characteristic to be excessively hard on the surface. Inconel is a registered trademark of Special Metals Corporation that refers to a family of austenitic nickel-chromium-based superalloys. Inconel alloys are typically used in high temperature applications. It is often referred to in English as "Inco" (or occasionally "Iconel"). CompositionDifferent Inconels have widely varying compositions, but all are predominantly nickel, with chromium as the second element.  PropertiesInconel alloys are oxidation and corrosion resistant materials well suited for service in extreme environments. When heated, Inconel forms a thick, stable, passivating oxide layer protecting the surface from further attack. Inconel retains strength over a wide temperature range, attractive for high temperature applications where aluminum and steel would succumb to creep as a result of thermally-induced crystal vacancies (see Arrhenius equation). Inconel's high temperature strength is developed by solid solution strengthening or precipitation strengthening, depending on the alloy. In age hardening or precipitation strengthening varieties, small amounts of niobium combine with nickel to form the intermetallic compound Ni3Nb or gamma prime (γ'). Gamma prime forms small cubic crystals that inhibit slip and creep effectively at elevated temperatures. MachiningInconel is a difficult metal to shape and machine using traditional techniques due to rapid work hardening. After the first machining pass, work hardening tends to elastically deform either the workpiece or the tool on subsequent passes. For this reason, age-hardened Inconels such as 718 are machined using an aggressive but slow cut with a hard tool, minimizing the number of passes required. Alternatively, the majority of the machining can be performed with the workpiece in a solutionised form, with only the final steps being performed after age-hardening. External threads are machined using a lathe to "single point" the threads, or by rolling the threads using a screw machine. Holes with internal threads are made by welding or brazing threaded inserts made of stainless steel. Cutting of plate is often done with a waterjet cutter. Internal threads can also be cut by single point method on lathe, or by threadmilling on machining center. New whisker reinforced ceramic cutters are also used to machine nickel alloys. They remove material at a rate typically 8X faster than carbide cutters. JoiningWelding inconel alloys is difficult due to cracking and microstructural segregation of alloying elements in the heat affected zone. However, several alloys have been designed to overcome these problems. The most common way to weld inconel is by using a TIG welder with the appropriate filler metal. UsesInconel is often encountered in extreme environments. It is common in gas turbine blades, seals, and combustors, as well as turbocharger rotors and seals, high temperature fasteners, chemical processing and pressure vessels, heat exchanger tubing, steam generators in nuclear pressurized water reactors, natural gas progressing with contaminants such as H2S and CO2, firearm sound suppressor blast baffles, and Formula One exhaust systems. North American Aviation constructed the skin of the X-15 rocket plane out of an Inconel alloy known as "Inconel X". Propeller Leading EdgeDuc uses a specific manufacturing process to insert an inconel leading edge in its blades:
Back to TOP Anodized AluminiumMany metals are structurally weakened by the oxidation process, but not aluminum. Aluminum can actually be made stronger and more durable through a process called 'anodizing'. Anodizing involves placing a sheet of aluminum into a chemical acid bath, quite often acetone in laboratory experiments. The sheet of aluminum becomes the positive anode of a chemical battery and the acid bath becomes the negative. An electric current passes through the acid, causing the surface of the aluminum to oxidize (essentially rust). The oxidized aluminum forms a strong coating as it replaces the original aluminum on the surface. The result is an extremely hard substance called anodized aluminum. Anodized aluminum can be nearly as hard as diamond under the right anodizing process. Many modern buildings use anodized aluminum in places where the metal framework is exposed to the elements. Anodized aluminum is also a popular material for making high-end cookware such as frying pans and pots. Heat is distributed evenly across anodized aluminum, and the process of anodizing provides a naturally protective finish. It is possible to use another electroplating process to make anodized aluminum look like copper or brass or other metals. Special dyes can also be used to color the anodized aluminum for decorative uses. Because of its strength and durability, anodized aluminum is also used in a number of other applications. Many of the satellites circling the Earth are protected from space debris by layers of anodized aluminum. The automobile industry relies heavily on anodized aluminum for trims and protective housings for exposed parts. Furniture designers often use anodized aluminum as the framework for outdoor pieces as well as the base metal for lamps and other decorative items. Modern home appliances and computer systems may utilize anodized aluminum as protective housing. Anodized aluminum may not be appropriate for all applications because of its non-conductive nature. Unlike other metals such as iron, the oxidation process doesn't seem to weaken aluminum. The layer of 'aluminum rust' is still part of the original aluminum and will not transfer to food or easily flake off under stress. This makes it especially popular for food-service applications and industrial applications where durability is crucial. Back to TOP MachineryClick to enlarge A high pressure press is used for the forge process of all the components. High temperature oil circulates into the mould during the polymerization. Click to enlarge  In 2007, the company business grew by 40%. A CNC machine has now been added to the assembly line in order to automate the milling and de-burring operations of the nose cones and the blades. The productivity of the assembly line now has an increased capacity and quality control is much more effective. Numerical control (NC) refers to the automation of machine tools that are operated by abstractly programmed commands encoded on a storage medium, as opposed to manually controlled via handwheels or levers or mechanically automated via cams alone. Analog and digital computers create the modern computer numerical controlled (CNC) machine tools that have revolutionized the design process. In this modern CNC system, end-to-end component design is highly automated using CAD/CAM programs. The programs produce a computer file that is interpreted to extract the commands needed to operate a particular machine, and then loaded into the CNC machines for production. The complex series of steps needed to produce any part is highly automated and produces a part that closely matches the original CAD design. Back to TOP ImplementationClick to enlarge The propeller hub is manufactured from impregnated carbon fibres. This process holds an international patent for forged carbon. Click to enlarge  Adjustment and fixation parts are made from anodised 2017 aluminium. Click to enlarge  Another key component, the spinner, is also made of pre-impregnated carbon fibre. The Turbo Spinner is another one of its kind innovation that improves greatly engine cooling during taxi and climb phases, thus increasing engine's life time. Click to enlarge  For the Turbo Spinner, the deflectors are also made of pre-impregnated carbon fiber. Click to enlarge  The result of all this high technology is an amazing assembly. Back to TOP TestingAll DUC products have been tested to demonstrate the superior resistance of Carbon Fiber parts. Testing of BladesTYPE OF ENGINEThe studies were carried out on 3 types of 4 stroke engines and on one type of 2 stroke engine.4 stroke engines:
2 stroke engines: ROTAX 582 with rotation / reduction gear box B 2.58, ROTAX 582 with rotation / reduction gear box C 2.62, ROTAX 582 with rotation / reduction gear box C 3, ROTAX 582 with rotation / reduction gear box C 3.47, ROTAX 582 with rotation / reduction gear box C 4. CALCULATION OF THE CENTRIFUGAL FORCEWe applied the following formula:F (N) = (M(kg) x V2 (m/s)) / R F : centrifugal force (N), M : blade ‘s weight (Kg), V : linear speed (m/s), R : Radius of the center of gravity (m). STATIC PULLINGClick to enlarge
It was impossible to obtain a complete rupture of the blade because of the tears around the attaching bolts of the system of traction. To estimate a value of rupture in the axis, we exerted an eccentric static traction of 32° .The rupture occurred on the level of the shoulder of blade’s foot. We can consider that the rupture of the blade in the axis represents approximately the double of the rupture’s value with 32° because with this position, only half of the blade’s foot is in contact with the assembly. The two tests with 32° were also carried out to observe the behavior of the blade subjected to combined pulling. These statements do not show to in no case reality being given that the centrifugal force is inevitably in the axis.
Read more about the Strength Test of the Swirl Back to TOP Testing of HubsThe three-bladed hub DUC HELICES is produced with the FORGED CARBON process, process which increases considerably the mechanical resistances of the composite parts. We realized in an office specialized two studies showing the advantages and the performances of the three-bladed hub DUC HELICES:
BETWEEN FORGED CARBON PROCESS AND AUTOCLAVE PROCESS The test-tubes tested were produced with the same material (class 180): Reference : T2H / 268 / 300 / EH25 / 35% Batch : 10108E01 Roller : 1009E001C  2 different shapes were used to ensure the validity of the results DRAPINGFORGED CARBON process:
RESULTSFORGED CARBON process: Curved edge ( type 1 )
Arris ( type 2 )
AUTOCLAVE process: Curved edge ( type 1 )
Arris ( type 2 )
Back to TOP CONCLUSION
BETWEEN FORGED CARBON HUB AND FORGED ALUMINIUM HUBThe objective of these tests is to evaluate the potential of parts made from the FORGED CARBON process. The composite half-hubs are compared to parts manufactured from 3 different aluminum grades. They are found to present comparable performances, while been much lighter. Back to TOP MATERIALS AND PARTSThe forged carbon half-hub has been manufactured with a aeronautical pre-impregnated carbon fiber of class 180.  FORGED CARBON ½ HUB  ALUMINIUM ½ HUB Carbon’s reference:
Draping:
Aluminum grades:
Weights:
Forged carbon: 270g
Forged carbon: 272g
Forged carbon: 268g
As well as carbon hubs are almost half the weight of aluminum ones expected, due to different material densities), we can see only few variation of their weight, from a part to another. Back to TOP TESTING PROCEDUREDifferent kind of loading have been tried. Up to now, we have examined 3 main cases: 1st case: Tension (up to about 15 kN), then compression (up to about 70 kN) of the hub along its symmetry axis 2nd case: Application of a momentum by tension along an axis bent from the symmetry one . Let’s call it symmetry axis bending. For these 2 cases, we have exploited the results in terms of apparent stiffness and fracture load when possible. Effectively, the load cell capacity being limited, we had to interrupt the best before breakage of the part in most of the cases. Also, we achieved several times failure of the bolts and nuts in the fastening tools during the test. The load and crosshead displacement only was measured, then we could observe a global stiffness of the part, taken on the linear portion of the curves. 3rd case:Compression along the hub symmetry axis, up to 100kN.We equipped the parts with strain gages on their plane flange, in order to obtain local strain state. (same apparatus as for 1st case) the specific performances of the parts have been obtained here by dividing the properties by the weight ofthe part. Back to TOP RESULTSFor tension and compression along the symmetry axis, no failure has been observed, either on aluminum or on composite hubs. 1st case:We can notice that the overall tension stiffness of the parts are comparable with those obtained with aluminum alloys. However, considering the lower weight of carbon parts, specific performances are much higher.2nd case:On this kind of test, the carbon parts show same or even higher stiffness than the aluminum ones. Except for the aluminum n°1 sample, failure load are of the same range. Failure mode seems to be less brittle for composites than or aluminum, and propagation occurs by delaminating of the plies. Also, specific values are higher for composites than for aluminum.3rd case:Compression with strain gages.Strain unit : 1μdef = 10-6 Back to TOP CONCLUSIONWe have seen that this process allows to manufacture shaped parts, with good health and respecting the reinforcement directions in the structure. The tested mechanical properties of the forged carbon hubs are comparable to those obtained from forged aluminum alloys, for similar parts dimensions, and hence better specific performances, thanks to the lower density of the material (1.5 compared to 2.9). Read more about the Strength Test of the Forge Carbon Hub |