As much of 50% of an Airbus A350X body can now be made from carbon fibre-reinforced polymer (CFRP), which lasers are particularly suited to processing (Image:Shutterstock/Chittapon Kaewkiriya)
The aerospace sector – which encompasses commercial and military aircraft, satellites, space vehicles, drones, and unmanned aerial vehicles (UAVs) – has undergone some seismic changes in recent years.
A proliferation of companies has entered the space race, many of whom require innovative manufacturing techniques for their technologies.
By contrast, the impact on commercial aviation of travel restrictions due to the pandemic led to a drop of one third in the rate of civil aircraft manufacturing.
In 2019, Europe was one of the world leaders in civil aeroplane and helicopter production (including various components, parts and aircraft engines), providing around 400,000 jobs and generating €130bn in revenue. While space exploration and defence were largely unaffected by the pandemic, civil aircraft production is still in the recovery stage.
In Planning for Uncertainty in Commercial Aerospace, published in February 2023, McKinsey reported a global backlog in orders of 9,400 passenger aircraft (mostly narrow-body jets) which need building before the end of 2027. But there is uncertainty in the future growth of passenger air travel and in the robustness of supply chains and the workforce. So manufacturers will need to become more productive and nimble to clear the backlog and respond to future changes in demand.
The ability of laser processing to increase productivity and keep costs low could play a crucial role in enabling such a response from the aerospace industry. Laser processing, in the form of cutting, welding, peening and drilling is integral to aerospace manufacturing. Lasers are used to produce flaps for aircraft wings, wing fasteners, parts of jet engines, and parts of seats, for example, as well as being employed to repair turbines, clean or strip paint from components, and prepare surfaces for further processing. Laser additive manufacturing (AM) is also gaining traction in the space flight sector, while there is an increasing requirement for laser marking of aerospace parts for traceability.
Laser cutting and welding
Laser cutting is a fast, cost-efficient and, most importantly, precise process that can be used to meet the stringent fabrication requirements of the aerospace sector. Compared with conventional machining, the accuracy of laser cutting results in less material waste, while the process is also faster, cheaper and the equipment needs less servicing. In addition, productivity is maximised because any required changes to the machining can be carried out quickly and readily.
It can be used in the production of wing fastener parts, fixture parts, end effector parts, tooling parts, and more. For example, it is equally suitable for small components such as grafoil gaskets and titanium bleed air duct manifolds, as for larger parts such as exhaust cones. It can process a wide range of aerospace materials including aluminium, Hastelloy (nickel that has been alloyed with elements such as molybdenum and chromium), Inconel, nickel alloys, nitinol, stainless steel, tantalum and titanium.
Laser welding is also used within the aerospace sector, as an alternative to conventional joining methods such as adhesive bonding and mechanical fastening. For example, using lasers to weld lightweight aluminium alloys and carbon fibre-reinforced polymer (CFRP) materials in airframe manufacture is of growing interest, being used to replace riveting wherever possible. Techniques such as laser wobble welding have also seen success in the joining of fuel tanks, where they offer improved joint efficiency, strength, reduced rework and substantial cost savings. Other welding successes in aerospace include joining the cast cores of turbine blades to cover plates, and creating new types of lightweight wing flap that offer increased laminar flow control – thereby minimising drag and optimising fuel efficiency.
Overall, laser welding has the potential to save costs, reduce the weight of components and improve weld quality compared with traditional methods, with several manufacturers now considering and even beginning to adopt laser welding for producing fuselage parts.
Laser cleaning for aerospace manufacturing
Manufacturers in the aerospace sector use laser cleaning to remove layers from the surfaces of metals and composites in order to prepare them for processing, to remove coatings or corrosion, and to strip paint off large components or entire aircraft before repainting them.
In the cleaning process, the laser ablates the surface material by being absorbed by the surface layer and vaporising it while having little effect on the material beneath and creating no collateral heat damage to the component. Pulsed fibre lasers in the kilowatt range are particularly suitable for fast laser cleaning – they can carry out the process with high levels of efficiency and precision on a wide range of materials including ceramics, composites, metals and plastics.
In recent years, the amount of composites used in aircraft has increased, and as a consequence so has the need for joining metals to composites. In aerospace manufacturing, adhesives can be used to join these two dissimilar materials, and in order to create strong bonds both surfaces must be carefully prepared before the adhesive is applied. Laser cleaning is ideal for this as it can create a very tightly controlled and reproducible surface landscape that allows for consistent and predictable bonding. Traditionally, this would be done via aggressive blasting techniques or several applications of chemicals. However, laser cleaning now offers a one-step approach that is not only more cost-effective and productive, but also has less impact on the environment, since no toxic chemicals or blasting materials are required. Laser cleaning is also much gentler on the component than such traditional methods.
When it comes to paint stripping, laser cleaning of metal and composite aircraft components is also more advantageous than chemical stripping or blasting techniques. Over its operational lifetime, an aircraft is likely to be repainted four or five times, and it can take a week or more to remove the paint from an entire aircraft using conventional techniques. By contrast, laser cleaning drops this to three or four days depending on the aircraft’s size. It also allows workers to reach parts more easily. In addition, when used for paint removal instead of chemical stripping or blasting, laser cleaning offers substantial cost savings – amounting to thousands of pounds for each aircraft since the hazardous waste is reduced by approximately 90% or more, bringing down material disposal requirements.
Laser peening
Stress within metal components can lead to metal fatigue failure in aircraft parts such as the fan blades of jet engines, which has the potential to cause damage or injury. This can be mitigated via a technique known as laser peening.
In this process, laser pulses are directed at an area of high stress concentration and each pulse ignites a tiny plasma explosion between the component’s surface and a water layer that has been sprayed on top. The water layer confines the explosion, which results in a shock wave that penetrates into the component and creates compressive residual stresses when it expands the region through which it travels. These stresses counteract cracking and other forms of metal fatigue. Compared with traditional processes, laser peening extends the service lifetimes of metal parts by 10-15 times.
Laser peening can mitigate stress on components such as jet engine fan blades (Image: Shutterstock/aappp)
Laser peening is seeing increasing adoption in the aerospace industry. For example, LSP Technologies and Airbus have together developed a portable laser peening system, which recently underwent testing and evaluation at Airbus’ maintenance and repair facilities in Toulouse, France. The Leopard Peening System will be used to extend fatigue life by inhibiting crack initiation and propagation caused by cyclic vibrational stresses. The flexibility of the fibre optic beam delivery and custom tools enables the system to laser peen hard-to-reach areas of an aircraft. According to the partners, the system is a breakthrough in laser peening technology that will advance its use – originally proven to extend the life of jet engine blades – to aircraft structures not currently being laser peened.
The US Navy’s Fleet Readiness Center East (FRCE) has also recently completed verification of a laser shock peening process, which has successfully been used on an F-35B Lightning II aircraft that has since returned to active service. The process was used by FRCE to strengthen the frame of the F-35 without adding any additional material or weight, which would otherwise limit its fuel or weapons-carrying capacity. This helps extend the life expectancy of the fifth-generation fighter, which is a short takeoff-vertical landing variant flown by the US Marine Corps.
Laser drilling
Modern aero-engines contain approximately 500,000 holes – around a hundred times more than engines built in the 1980s. Aircraft manufacturers are also producing increasing quantities of a range of other components with a high number of drilled holes for riveted and screwed joints. Therefore, for aviation in particular, laser drilling has enormous market potential, offering a precise, repeatable, fast and cost-efficient process.
For instance, new high-power femtosecond laser systems are being developed for highly productive yet precise micro-drilling of holes into large titanium HLFC (hybrid laminar flow control) panels destined for mounting on wings or tail stabilisers. These panels lower fuel consumption thanks to sucking air through the small holes and thereby reducing frictional drag.
Lasers are being increasingly used to drill holes in CFRP aircraft components (Image: Laser Zentrum Hannover)
Due to laser drilling being contact-free, the processed material does not need to be secured in the same way as if it were machined with conventional tools. Another advantage of being contact-free is that no tool-wear is experienced, which represents a particular advantage when drilling CFRP components, which, due to their hardness, produce an exceptionally large amount of wear on traditional tooling. Laser drilling can also be carried out at very high speeds, so excess damage from heat is not inflicted on the material being processed.
Additive manufacturing
Laser additive manufacturing (AM), in which lasers melt successive layers of powder to build up the shape, is also gaining rapid traction in the aerospace industry. A leading California-based rocket company even recently ordered two 12-laser 3D printers to make its space missions more affordable and efficient by creating lighter, faster, and more robust space components.
While a lot of projects are still in the test stage, laser AM has already been successfully used on two Mars missions. NASA’s Curiosity rover, which landed in August 2012, was the first mission to carry a 3D-printed part to Mars. This was a ceramic component inside its Sample Analysis at Mars (SAM) instrument, and was part of an ongoing testing programme to investigate the reliability of AM technologies.
A bimetallic combustion chamber with GRCop-42 L-PBF liner and Nasa HR-1 LP-DED jacket made by Nasa (Image: NASA)
Meanwhile, NASA’s Perseverance rover, which touched down on the red planet in February 2021, contains 11 metal parts made with laser AM. Five of these parts are in Perseverance’s Planetary Instrument for X-ray Lithochemistry (PIXL) instrument, which is searching for signs of fossilised microbial life on Mars. These components needed to be so lightweight that conventional techniques such as forging, moulding, and cutting could not have produced them.
NASA has also been experimenting with using laser AM to manufacture rocket components. In one study, a rocket engine combustion chamber was fabricated from a copper alloy. Continued development of this laser AM has resulted in that component being created for roughly half the cost and in a sixth of the time required by traditional machining, joining and assembling. Since the copper alloy used is highly reflective of IR lasers, NASA is now looking at how green or blue lasers could improve efficiency and productivity.
Although the use of additive manufacturing in aerospace is currently at an early stage, growth is expected over the next 20 years.
Laser texturing
Laser texturing is also a very new application being explored in the aerospace industry. Here, ultrafast lasers are used to produce micro- and nanostructures on the surfaces of aircraft via a technique known as direct laser interference pattern (DLIP), which is used to produce a natural ‘lotus effect’ that helps prevent surface contamination.
Laser nanostructuring can prevent ice buildup on aircraft by repelling water (Image: Shutterstock/Media_works)
Innovative optics split one powerful ultrafast laser pulse into several partial beams, which are later combined on the surface being processed. The microstructures that are generated, when viewed under a microscope, resemble microscopic halls of pillars or corrugated iron roofs. The distances between the pillars can be between approximately 150nm and 30µm. Such structures mean that water droplets no longer wet the surface and stick to it as they do not have enough grip on the surface.
The advantages of this for aircraft include increased repellence of water, ice and insects, which can all stick to the surface of an aircraft, increasing its wind resistance and thus fuel consumption. Applying such laser textures will reduce the need for toxic chemical treatments currently applied to the surface of aircraft to avoid icing, which are known to age over time and damage easily. In addition, laser structures produced by the DLIP method can last years and do not raise environmental concerns.
