A new fibre-overbraiding technique has the potential to improve efficiency in the production of composite structures. A new simulation programme reduces costly trial runs with the modern overbraiding machine.
NLR is assisting company Eurocarbon with the refinement of braiding technology used to produce hollow composite structures. The project – ‘Innovating the overbraiding design process to optimise the development of composite aircraft structural components’ (OBODAS) – focuses mainly on efficiency. The simulation programme will enable Eurocarbon to achieve significant savings in development and production costs for composite structures. On paper, the principle of overbraiding is simple: a machine equipped with dozens of spools, wraps fibres around a mould that is shaped like the composite component to be produced. The fibre form is then impregnated with resin, which results in the composite structure. But the process has drawbacks. The shape of the structure can affect the distribution of the fibre layers and thus in turn alter the material properties of the entire composite structure. To counteract these adverse effects, the braiding machine has to undergo trial runs to determine the correct settings. These tests are costly in terms of both labour and material. This is where the results of the OBODAS project are helpful.
NLR engineers based the development of this simulation environment on Knowledge Based Engineering techniques, applying available knowledge of the overbraiding process to simulate and optimise all aspects of the process. The data generated by the simulation programme can be directly converted into settings for the overbraiding machine. Trials with the simulation programme, including the user interface, have already confirmed that OBODAS works effectively.
In the OBODAS project, NLR worked in collaboration with the University of Twente and Eurocarbon. The project was supported by NL Agency of the Dutch Ministry of Economic Affairs.
Towards automation of composites manufacturing
The Automated Composites Manufacturing Technology Centre (ACM-TC) was established in 2004 at the National Aerospace Laboratory in the Netherlands (NLR) to prepare the way towards automated manufacturing of advanced composite structures, largely in support of the "composites" industry, but also of enterprises, which are new to this material. The centre brings together the complementary research capabilities of research centres, universities and specialised small enterprises and a consortium has been formed of industries as members.
Pioneer technology to achieve competitiveness
The vision of the ACM-TC is "to pioneer innovative fabrication technologies for composites with potential for automation" and thereby "to enhance the competitiveness of its members", by conducting applied research and carry out development programmes up to the level of full scale prototypes.
A co-operation of partners with complementary capabilities
ACM-TC is a co-operation formed by partners and members. Partners are offering services and facilities to help the industry prepare for automated composites manufacturing by contributing to or carrying out R&D projects. Members are industries, which are actively pursuing new automation technologies to manufacture composite structures. Co-operation is not limited to the national scale, ACM-TC is eager to extend the co-operation internationally.
Develop insight in fabrication technologies
The primary aim of ACM-TC is to develop the insight in automated composites manufacturing techniques that industries need before they can apply new technologies to their particular applications. This is achieved by providing the expertise and facilities that are essential for the development of automated manufacturing technologies for advanced composites. Thereby, most aspects with regard to the implementation of the technology at the industry can be covered before large investments are being made. Fabricating full-scale prototypes and pre-series can validate new concepts.
Complex composites lighten NATO copter
Dutch consortium develops advanced composite critical landing gear that meets NH90 helicopterperformancerequirements.
• Lighter and stronger than existing metal design
• Braided reinforcement permits preform automation
• Performance testing validates finite element analysis predictions
The application of carbon fiber composites to the wings and fuselage of a newly designed aircraft is now standard practice. One area of aircraft design that continues to elude the composites community, however, is the landing gear. As primary structural elements with concentrated loads, conservativedesign practice has traditionally dictated metal in these components. This may change if a team of Dutch companies and scientists is successful in its quest to design and fabricate lightweight, durable composite landing gear for heli-copters and fixed wing aircraft. SP aerospace and vehicle systems (Geldrop, The Netherlands) is under contract for the development, qualification and production of a retractable, crashworthy NH90 Rear Landing Gear Assembly landing gear for the NATO NH90 helicopter, in both Army (TTH, or Tactical Transport Helicopter) and Navy (NFH, or NATO Frigate Helicopter) versions. A joint development of Eurocopter (France and Germany), Agusta (Italy) and Fokker (The Netherlands), this 10-ton-class helicopter will be used for a wide variety of tasks, such as troop transport, cargo transport and anti-submarine operations. Composites are widely used throughout the helicopter, such as in the airframe, stabilizers, and the rotor blades. Development prototypes of the helicopter have been flying since 1995 and the first serial production delivery is scheduled for 2004. The NATO Helicopter Management Agency (NAHEMA), consisting of France, Germany, Italy, The Netherlands and Portugal, has ordered 253 helicopters with an option for 124 more. The Nordic countries (Sweden, Finland and Norway) have ordered 52 units, with an option for an additional 17. The landing gear is currently designed in metal. In the mid-1990s, SP aerospace, in conjunction with the Structures and Materials Division of the Netherlands National Aerospace Laboratory, NLR (Amsterdam, The Netherlands) began exploring the use of advanced composites, convinced that composites technology had matured to a point where a landing gear application was practical, according to René Hekerman, engineering manager for SP aerospace. In 1996, the team initiated a technology development project to design, build and validate carbon fiber composite torque links and a trailing arm assembly based on NH90 landing gear specifications. SP aerospace is the lead company for the project, responsible for concept design component specifications, integration of components into the landing gear, and component testing and qualification. NLR is handling the conceptual design for the composite elements, development of design allowables, development and manufacture of the RTM production molds and the composite parts, and subsequent testing of the subcomponents. Two additional partners provide specific expertise: Eurocarbon (Sittard, The Netherlands) has responsibility for the development of a fully automated overbraiding technique for the fabrication of cost-effective preforms for the composite trailing arms, while MSG Software Benelux BV (Gouda, The Netherlands) provides the finite element analysis (FEA) of the mechanical strength of the composite structures.
Funded by the Dutch Government and the partners themselves, the program is split into two phases: technology development and validation. The torque link was developed from 1996 to 1999. This relatively simple component was used as a demonstrator in order to bring the design, analysis and RTM capabilities to a higher level. This enabled development of the trailing arm's very complex shape, which was had its beginnings in 1998 and was largely completed in 2002.