As a pioneer in composite blade technology, Dowty Propellers has unmatched expertise in the design, development, production and support of its products – which are used in front-line military airlifters, regional airliners and marine hovercraft vehicles.
Propellers are particularly well suited for the application of composites, as materials such as glass and carbon fiber polymers provide lightweight blades with high specific strength and stiffness, as well as resistance to centrifugal forces and aerodynamic loading.
Since the 1970s, Dowty Propellers has continuously evolved and perfected its resin transfer molding (RTM) techniques – the basis from which all of the company’s composite blade designs have been developed. Advantages of its RTM design – which utilizes carbon fiber for the load-carrying spars along with carbon and glass fiber for the blade skin profiles – include close control of part thickness and fiber content, along with the ability for one-shot molding of complex parts.
Outer fiber layers for the propeller blade skin are applied in a braiding process, for which Dowty Propellers’ operates two braiding machines capable of both bi-axial and tri-axial braiding. The braiding process offers multiple advantages compared with normal composite fabric lay-up assembly, including rapid production rates, along with the ability to mix carbon and glass fibers for the required strength and resistance properties. In addition, the braided skin has a higher impact resistance and more consistent quality than when produced by hand lay-up assembly.
Dowty Propellers also has extensive experience in the other skills required for the production of composite blades, from tooling design and bonding techniques to methods of attaching the blade to its metal root.