On the silent wings of freedom

In a ground-breaking feat of complex engineering, Norco Composites demonstrates its expertise in out-of-autoclave composite manufacturing for the wing frames of an unmanned aerial vehicle (UAV) project.

 

Dorset-based Norco Composites says it has built up a reputation for delivering large complex composite structures. The company has expanded its capability to be able to offer a complete composite manufacturing service, from CAD design and engineering, through tool-design to the manufacture of finished components using a variety of composite processes.

It is this expertise, and depth of capability, that recently led a new, unnamed customer to commission Norco to work on a project that will have repercussions on a worldwide scale.

The project is to manufacture all the primary composite structures for a battery and solar powered unmanned aerial vehicle (UAV) that is being developed by the customer. The complexity of the project was ground-breaking, with the need for Norco to develop industry-leading techniques using ultra-light materials and deliver the first set of wing-frames in just nine months.

Due to the complex requirements for multiple sections that formed the UAV assembly, Norco worked extensively with the customer at the design for manufacture stage. The ability for Norco to contribute at this early stage of the project was critical in its success and resulted in a certified first article which undertook test flying.

Removing the autoclave bottleneck

One of the key benefits Norco has been able to demonstrate is its expertise in out-of-autoclave composite manufacturing. Many aerospace applications require autoclave processing to maximise the material characteristics and retain the required strength and low void content. However, autoclave processing is expensive and often limited by size, and so Norco’s capability to achieve the required solution using low temperature prepreg - combined with careful processing methods and carbon fibre-reinforced CNC direct mould tools - has been invaluable.

Maximum weight reduction, surface finish off the tool and geometric tolerances were three primary requirements for the UAV. This led Norco to undertake a significant review of potential composite materials and processing techniques, whilst researching and testing the lightest fabrics on the market. The first finished complete 42m UAV weighed just 160kg and after an intensive optimisation programme into weight reduction this figure was reduced to 120kg, whilst at the same time increasing overall stiffness to avoid natural frequency issues and ‘flutter’ which is a commonly known catastrophic failure mode in large flying structures. The UAVs were designed to continuously fly for up to three months at a time, at an altitude in excess of 60,000ft, but also designed with joints that catered for disassembly and packing into 40ft containers.

The first UAV prototype was produced by Norco in under nine months including design and tooling. Subsequent production of additional UAVs continued after the launch flight of the prototype. In order to keep up with expected production volumes, Norco invested in a dedicated facility at its Poole manufacturing site with a bespoke 9m x 5m composite curing oven where it continues to produce component parts. Norco also supported the customer by sending key personnel to its location in the US to help support and train local engineers in repair techniques.

Having completed a tranche of pre-production prototypes, Norco was then contracted by the customer to work with them on a revised design. As well as further research on alternative materials, this phase involved a significant R&D project. Focused on tooling, the challenging goal was to manufacture primary structures in single sections without adhesive joints. A tooling process was developed enabling double A-surfaces, no adhesive joints, no fabric wrinkling, continuous sandwich construction and a design that wasn’t restricted by negative draft angles.

The UAV project has clearly demonstrated Norco’s ability to manufacture complex composite solutions. It also showcases Norco’s commitment to investing in both R&D and facilities to offer an unparalleled level of ‘design for manufacture’ service to customers.

www.norco.co.uk

Company

Norco Group

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