State-owned aeronautics company Denel Aerostructures says it has put a number of measures in place to ensure that it consistently produces high-quality components for its clients, which include major aircraft manufacturers Airbus, Boeing, AgustaWestland and Gulfstream.
Denel Aerostructures CEO Ismail Dockrat tells Engineering News that composites have become a mature technology in the aerospace industry.
“Over the past few years, we have established ourselves as a world-class composites supplier and have invested significantly in our composites manufacturing facility, which is now comparable to some of the best facilities in the world,” he states.
Denel Aerostructures’ composites facility manufactures lightweight, efficient and cost-effective aircraft structures, such as wing-to-fuselage fairings and top shells, which are supplied to European aerospace and defence company Airbus Military for the A400M aircraft.
“Being one of the few companies outside Europe and North America to supply components to one of the biggest aircraft manufacturers in the world is a significant achievement for us and Africa,” says Dockrat.
Denel Aerostructures has also supplied air- craft structures to US-based multinational aerospace and defence corporation Boeing, British-Italian helicopter manufacturer AgustaWestland and business jet manufacturer Gulfstream Aerospace Corporation.
Denel Aerostructures production man- ager Alan Robertson says an important com- ponent of the composites facility is the machinery it uses, as well as the high level of hand skills required to produce its com- posite components.
“A challenge for companies that want to manufacture and supply composite aerospace material-based products is the signifi- cant price tag associated with establishing the facility. Autoclaves cost in the region of R10-million each.
“The capital outlay for a cleanroom is also expensive, considering that the rooms are controlled by temperature, humidity and pressure. The latest technology is required to achieve consistent levels,” he adds.
Further, a five-axis CMS machine, which cuts the aircraft panels to the correct dimensions, costs about R35-million.
“When dealing with a large company like Airbus, all critical machines are required to be duplicated for backup in the case of break-downs and maintenance.
“We have also invested in Metronor measuring equipment, which measures the accuracy of the manufacturing process. Some of these specifications are extremely complex and suitable tools are needed to achieve the correct measurements. Denel Aerostructures uses nondestructive testing and ultrasonic equipment to inspect possible delaminating and any other defects on our composite panels,” says Robertson.
He adds that the tooling is expensive, as the specifications that the production team receives from the engineers must be strictly adhered to for a high- quality finish.
Denel Aerostructures uses carbon fibre-reinforced plastic (CFRP) as one of its composite materials.
“CFRP is lighter than aluminium, stronger than iron and has a higher elasticity than titanium. The material is increasingly being used in the aerospace industry. Carbon is mainly used in the aircraft industry because of its high stiffness-to-weight ratio, as well as its strength-to-weight ratio, explains Denel Aerostructures chief engineer Alcino Cardoso.
He says components are manufactured by layering partially cured resin-impregnated fibres, which can be stiffened with honeycomb core and fully cured in an autoclave, under pressure and temperature.
Meanwhile, Dockrat explains that raw materials, such as copper mesh, Kevlar mesh and fibre- glass, which are other materials used by Denel for its composites technologies, are kept at a set temperature to avoid the materials from curing.
“These raw materials are of a high specification to meet the requirements of the aerospace industry, and must be kept at –18 ºC. Failing to do so will result in the raw materials curing and having no further use.”
Further, Cardoso explains that these raw materials can only be kept outside the freezers for a certain amount of time, as temperatures higher than –18 ºC affect the chemical reaction of the raw materials, resulting in them becoming hard and, ultimately, unable to mix with other materials.
Meanwhile, Robertson notes that the company provides training through its apprenticeship programme.
“Composites are the future of manufacturing materials and people need to be trained so that when the composites industry grows, people will be familiar with the technology and even be in a position to develop and improve it,” he says.
Dockrat points out that Denel Aerostructures is optimistic about its composites facility being a source of knowledge and experience for other industries. “We have been in the composites business for some time now and composite materials have properties that make this industry’s inevitable growth imminent.
“We hope to share this knowledge with other industries and, in doing so, create more jobs,” he states.