In recent years, the aerospace sector - including commercial and military aircraft, satellites, spacecraft, drones and unmanned aerial vehicles (UAVs) - has undergone some sweeping changes. A growing number of companies have joined the space race, many of which require innovative manufacturing technologies.
In contrast, the impact of pandemic-caused travel restrictions on commercial aviation has led to a one-third drop in civil aircraft manufacturing rates.
In 2019, Europe was one of the global leaders in civil aircraft and helicopter production (including various components and aircraft engines), providing some 400,000 jobs and generating €130 billion in revenue. While space exploration and defense are largely unaffected by the New Crown pandemic, civil aircraft production and manufacturing are still in the recovery phase.
In its February 2023 publication, Uncertainty in Commercial Aerospace, leading consulting and research firm McKinsey reports that the world needs to absorb a backlog of orders to build 9,400 passenger aircraft (mainly narrow-body jets) by the end of 2027. But there is uncertainty about the future growth of air passenger transport, the supply chain and the soundness of the workforce. As a result, manufacturers need to improve productivity and flexibility to handle the backlog and respond to future changes in demand.
Laser processing's ability to increase productivity and keep costs low may play a key role in enabling this response in the aerospace industry. Laser processing - in the form of cutting, welding, shot peening and drilling operations - has become an integral part of aerospace manufacturing.
For example, lasers are used to manufacture aircraft wing flaps, wing fasteners, jet engine components and seat parts, as well as to repair turbines, clean or remove paint from parts and prepare component surfaces for further processing. In recent years, laser additive manufacturing (AM) has also become increasingly popular in the aerospace flight sector. In addition, the market wants to improve the traceability of aerospace components, and with that, the demand for laser marking is increasing.
Laser cutting and welding
Laser cutting is a fast, cost-effective and precise process that can be used to meet the demanding manufacturing requirements of the aerospace sector.
Compared to traditional processing, laser cutting offers high accuracy, less material waste, faster processing speeds, lower costs and less equipment maintenance. In addition, productivity can be maximized because it allows any necessary changes to the process to be made quickly and easily.
The laser can be used to produce wing fastener parts, fixture parts, end-effector parts, tooling parts, etc. It is equally suitable for small parts, such as graft oil gaskets and titanium pilot tube manifolds, as well as larger parts, such as exhaust cones. It can process a variety of aerospace materials, including aluminum, Hastelloy (nickel that has been alloyed with elements such as molybdenum and chromium), Inconel, Nitinol, Nitinol, stainless steel, tantalum and titanium.
Laser welding is also used in aerospace as an alternative to traditional joining methods, such as adhesive bonding and mechanical fastening. For example, the use of laser welding of lightweight aluminum alloys and carbon fiber reinforced polymers (CFRP) in aircraft manufacturing are increasingly valued and are being used wherever possible to replace riveted joints. Technologies such as laser swing welding have also been successful in fuel tank connections, improving the efficiency and strength of the connection, reducing rework and providing significant cost savings. Other welding successes in aerospace include attaching cast cores of turbine blades to covers; and creating new types of lightweight wing flaps that increase laminar flow control, minimize drag and optimize fuel efficiency.
With the potential for cost savings, component weight reduction and improved weld quality compared to traditional methods, several manufacturers in the market are even now considering laser welding for airframe parts.
Laser cleaning
Manufacturers in the aerospace sector use laser cleaning to remove layers from metal and composite surfaces in preparation for machining, to remove coatings or corrosion, and to remove paint from large parts or entire aircraft before repainting.
During the cleaning process, the laser light is absorbed and evaporated by the surface layer of metal, resulting in ablation of the surface material with little to no effect on the inner layer and no collateral thermal damage to the component. Kilowatt-class pulsed fiber lasers are particularly well suited for rapid laser cleaning - they can clean a wide range of materials, including ceramics, composites, metals and plastics, with high efficiency and precision.
The use of composites in aircraft has increased in recent years, and so has the need to join metals to composites. In aerospace manufacturing, adhesives can be used to join these two different materials, and in order to create a strong bond, the two surfaces must be carefully prepared for processing before the adhesive is applied.
Laser cleaning is the ideal option because it creates a very tightly controlled, reproducible surface effect that is capable of achieving a consistent, predictable bond. Traditionally, this would be accomplished through destructive blasting techniques or the application of several chemicals. However, laser cleaning now offers a one-step approach that is not only more cost effective and productive, but also has a much lower environmental impact as no toxic chemicals or blasting materials are required. Laser cleaning is also much gentler on parts than traditional methods.
Laser cleaning of metal and composite aircraft components is also more beneficial than chemical stripping or blasting techniques when it comes to paint stripping. During its lifetime, an aircraft may be repainted 4-5 times, and it may take a week or more to remove paint from an entire aircraft using traditional techniques. In contrast, laser cleaning can reduce this time to 3-4 days, depending on the size of the aircraft, and it also gives workers easier access to the parts. In addition, when used for paint removal rather than chemical stripping or blasting, laser cleaning can result in significant cost savings - thousands of pounds per aircraft - because hazardous waste is reduced by about 90% or more and material handling requirements are reduced.
Laser Blasting/Laser Impact Peening
Stresses within metal components can lead to metal fatigue failure in aircraft components such as fan blades in jet engines, which can potentially cause damage or injury. This can be mitigated by a technique known as laser peening.
In this process, laser pulses are directed to an area of high stress concentration, and each pulse ignites a tiny plasma blast between the component surface and a layer of water sprayed on top. The water layer confines the blast, which causes the shock wave to penetrate the component and generate compressive residual stresses as its propagation area expands. These stresses counteract cracking and other forms of metal fatigue. Laser peening can extend the service life of metal parts by 10-15 times compared to conventional processes.
Laser peening is increasingly being used in the aerospace industry. For example, LSP Technologies and Airbus have jointly developed a portable laser peening system that was recently tested and evaluated at Airbus' maintenance and repair facility in Toulouse, France.
The Leopard laser peening system will extend fatigue life by inhibiting the emergence and expansion of cracks caused by cyclic vibration stresses. The flexibility of fiber optic beam delivery and custom tooling allows the system to laser hard-to-reach areas of the aircraft. According to the partners, the system is a breakthrough in laser peening technology and will advance its use, including extending the life of jet engine blades, among other things.
U.S. Navy Fleet Readiness Center East (FRCE) also recently completed validation of a laser impact strengthening process that has been successfully used on the F-35B Lightning II aircraft. FRCE used the process to strengthen the F-35B Lightning II's frame without adding any additional material or weight that would otherwise limit its fuel or weapons-carrying capability. This helps extend the life expectancy of the fifth-generation fighter, the short takeoff and landing version used by the U.S. Marine Corps.
Laser Drilling
Modern aero engines have about 500,000 holes, about 100 times the number of engines built in the 1980s. At the same time, aircraft manufacturers are producing more and more other components that have a large number of drilled holes for riveted and screwed connections. Laser drilling therefore has a huge market potential in the aerospace sector because it offers a precise, repeatable, fast and cost-efficient process.
For example, new high-power femtosecond laser systems are being developed for efficient and precise micro-drilling of large titanium HLFC (Hybrid Laminar Flow Control) panels that will be mounted on wing or tail stabilizers. These panels draw air through small holes, thereby reducing frictional drag and lowering fuel consumption.
Image Lasers are increasingly used for drilling CFRP aircraft components
(Image credit: Laser Center Hannover)
Since laser drilling is contactless, the material being processed does not need to be held in the same way as if it were being processed with conventional tools. Another advantage of the contactlessness is that no tool wear occurs, which represents a particular advantage in the operation of drilling CFRP components. Due to their hardness, CFRP components can cause very high wear on conventional tools. Laser drilling can also be performed at very high speeds, so that excessive damage from heat does not harm the material being processed.
Additive Manufacturing
Laser additive manufacturing (AM) is also gaining rapid momentum in the aerospace industry. In this technique, a laser melts continuous layers of powder to build shapes. A California-based rocket company even recently ordered two 12-laser beam 3D printers to make its space missions more economical and efficient by creating lighter, faster and stronger space components.
While many projects are still in the testing phase, laser additive manufacturing has been used successfully on two missions to Mars. NASA's Curiosity rover, which landed in August 2012, was the first mission to carry 3D printed parts to Mars. This is a ceramic component inside the Sample Analysis on Mars (SAM) instrument, part of an ongoing testing program to investigate the reliability of additive manufacturing technology.
Meanwhile, NASA's Trailblazer rover, which lands on Mars in February 2021, contains 11 laser additive manufactured metal parts. Five of the parts are in Trail's Planetary Instrument for X-ray Lithochemistry (PIXL), which is looking for signs of microbial fossil life on Mars. These parts need to be so light that they cannot be produced by traditional forging, molding and cutting techniques.
NASA has also been experimenting with laser additive manufacturing of rocket components. In one study, the combustion chamber of a rocket engine was made from a copper alloy. This continued development of laser additive manufacturing has resulted in a component that can be manufactured at about half the cost and one-sixth the time required for traditional machining, joining, and assembly. Because the copper alloys used are highly reflective of infrared lasers, NASA is now investigating how green or blue lasers can improve efficiency and productivity.
While the use of additive manufacturing in aerospace is still in its early stages, it is expected to grow over the next 20 years.
Laser grossing
Laser grossing is also a very new application in the aerospace industry. In this process, ultrafast lasers are used to create micro-nanostructures on aircraft surfaces through a technique known as direct laser interferometric patterning (DLIP), which is used to create a natural "lotus effect," creating nanostructures that help prevent surface contamination and ice buildup on the aircraft.
The innovative optics split a powerful ultrafast laser pulse into several partial beams, which are then combined on the surface being processed. When viewed under a microscope, the resulting microstructure resembles a microscopic "hall" of "pillars" or ripples. The distance between the "pillars" is between about 150nm and 30µm - a structure that means water droplets no longer wet the surface and stick to it because they don't have enough grip on the surface.
The benefits of this material for the aircraft include increased repulsion of water, ice and insects. These can stick to the surface of the aircraft and increase the aircraft's resistance to wind, thus increasing fuel consumption. The application of this laser texture will reduce the need for toxic chemical treatments currently applied to aircraft surfaces to avoid icing. It is known to deteriorate over time and is prone to damage. Furthermore, laser structures produced by the DLIP method can last for several years and do not cause environmental problems.
