Thesector - including commercial and satellite, spacecraft, drones and unmanned aerial vehicles (UAVs) - has undergone some radical changes in recent years. More and more companies are joining the space race, and many of them need innovative manufacturing techniques.
Laser processing's ability to increase productivity and keep costs low may play a key role in realizing this response from theindustry. Laser processing - which realizes operations in the form of cutting, welding, blasting and drilling - has become an integral part ofmanufacturing.
For example, lasers are used to manufacture flaps, wing fasteners, jet engine components, and seat parts for airplane wings, 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 gained popularity in the space flight sector. In addition, the market is looking to improve the traceability ofcomponents, 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 thesector.
Compared to conventional processing, laser cutting offers high precision, less material waste, faster processing speeds, lower costs and less equipment maintenance. In addition, it maximizes productivity because it is quick and easy to make any necessary changes to the machining.
Laser can be used to produce wing fastener parts, fixture parts, end-effector parts, tooling parts, and more. It is equally suited to smaller parts, such as grafted oil gaskets and titanium pilot tube manifolds, as well as larger parts, such as exhaust cones. It can process a wide variety ofmaterials, 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 inas 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 materials that are gaining in importance and are being used to replace riveting wherever possible. Techniques such as laser pendulum welding have also been successful in fuel tank joining, improving the efficiency and strength of the joints, reducing rework and providing significant cost savings. Other welding successes ininclude 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, part weight reduction and improved weld quality over traditional methods, several manufacturers in the market today are even beginning to consider laser welding for airframe parts.
Laser Cleaning
Manufacturers in thesector use laser cleaning to remove layers from metal and composite surfaces in preparation for processing, to remove coatings or corrosion, and to remove paint from large parts or entire airplanes prior to repainting.
During the cleaning process, the laser light is absorbed and evaporated by the surface layers of the metal, resulting in ablation of the surface material with little or no effect on the inner layers and no collateral thermal damage to the component. Pulsed fiber lasers in the kilowatt class are particularly well suited for rapid laser cleaning - they allow efficient, high-precision cleaning of a wide range of materials, including ceramics, composites, metals and plastics.
The use of composites in aircraft has increased in recent years, and so has the need to attach metals to composites. Inmanufacturing, adhesives can be used to join these two different materials, and in order to create a strong bond, both surfaces must be carefully prepared for machining before the adhesive is applied.
Laser cleaning is the ideal option as it creates a very tightly controlled, replicable surface finish 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 less impact on the environment as no toxic chemicals or blasting materials are required. The impact of laser cleaning on parts is also much gentler than traditional methods.
Laser cleaning of metal and composite aircraft parts is also more favorable than chemical stripping or blasting techniques when it comes to paint stripping. An aircraft may be repainted 4-5 times during its lifetime, and it can take a week or more to remove paint from an entire aircraft using traditional techniques. In contrast, depending on the size of the aircraft, laser cleaning can reduce this time to 3-4 days, and it also makes it easier for workers to access 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 - due to a reduction in hazardous waste of around 90% or more and reduced material handling requirements.
Laser Shot Peening/Laser Impact Peening
Stresses within metal components can lead to metal fatigue failure in aircraft components (such as fan blades in jet engines), which has the potential to cause damage or injury. This can be mitigated by a technique known as laser peening.
In this process, laser pulses are directed into an area of high stress concentration, and each pulse ignites a tiny plasma explosion between the surface of the component and a layer of water sprayed on top. The water layer confines the explosion, which causes the shock wave to penetrate the component and creates compressive residual stresses as its propagation region expands. These stresses improve the likelihood of cracking and other forms of fatigue resistance in metals. Laser peening can extend the service life of metal parts by a factor of 10-15 compared to conventional processes.
Laser blasting is increasingly used in theindustry. 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 stress. The flexibility of fiber optic beam delivery and customized tooling allows the system to laser beam areas that are difficult for aircraft to reach. According to the partners, the system is a breakthrough in laser peening technology that will advance its use, including extending the life of jet engine blades, among other things.
Laser drilling
Modern aero-engines have about 500,000 holes, about 100 times as many as engines built in the 1980s. At the same time, aircraft manufacturers are producing an increasing number of other components that have a large number of holes drilled for riveted and screwed connections. In thesector, therefore, laser drilling has great market potential because it offers a precise, repeatable, fast and cost-effective 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, which reduces frictional drag and lowers fuel consumption.
Since laser drilling is contactless, the material being processed does not need to be fixed in the same way as if it were processed with conventional tools. Another advantage of being contactless 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 be very abrasive to 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 rapidly growing in theindustry. In this technique, a laser melts successive layers of powder to build shapes. A California-basedcompany even recently ordered two 12-laser-beam 3D printers to make its space missions more cost-effective and efficient by creating lighter, faster, and stronger space components.
While many of these projects are still in the testing phase, laser additive manufacturing has already been used successfully on two missions to Mars. NASA's Curiosity rover, which landed in August 2012, was the first mission to Mars to carry 3D printed parts. This is a ceramic component within the Sample Analysis for Mars (SAM) instrument, part of an ongoing test program to investigate the reliability of additive manufacturing technology.
NASA-built bimetallic combustion chamber with GRCop-42 L-PBF gaskets and Nasa HR-1 LP-DED sheathing
Meanwhile, NASA's Perseverance rover, which landed on Mars in February 2021, contains 11 metal parts made with laser additive manufacturing. Five of these parts are in Perseverance's Planetary Instrument for X-ray Petrochemistry (PIXL), which is looking for signs of microbial fossil life on Mars. These parts need to be so light that they cannot be produced using traditional forging, molding and cutting techniques.
NASA has also been experimenting with the use of laser additive manufacturing forcomponents. In one study, the combustion chamber of aengine 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 in one-sixth the time required for conventional 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 additive manufacturing applications inare currently in their early stages, they are expected to grow over the next 20 years.
Laser Grossing
Laser grossing is also a very new application in theindustry. In this process, ultrafast lasers are used to create micro- and nanostructures on aircraft surfaces through a technique known as direct laser interference patterning (DLIP), which is used to create a natural "lotus effect" that creates nanostructures that help prevent surface contamination as well as 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 microstructures resemble microscopic "halls" of "pillars" or ripples. The distance between the "pillars" is between about 150 nm and 30 μm - this structure means that 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 aircraft include increased repulsion of water, ice and insects. These can stick to the surface of the aircraft and increase the wind resistance of the aircraft, thus increasing fuel consumption. Application of this laser texture would reduce the need for toxic chemical treatments currently applied to aircraft surfaces to avoid icing. It is known to age over time and is susceptible to damage. Furthermore, laser structures produced with the DLIP method can last for years and do not cause environmental problems.
Laser Inspection and Stress Regulation
In addition to the above functions, the combination of laser and ultrasound can be used for the inspection and stress regulation of complex metal structural components. The use of high-energy pulsed laser action on the surface of the object to be tested, the surface of the local temperature changes, which causes the object to be tested in the surface layer of thermal expansion, the excitation of ultrasound, ultrasound will carry the material surface and the internal useful information, ultrasound signals with a detector to receive, the data processing and analysis of the object to be examined in order to determine the presence or absence of defects.
In addition, due to the laser ultrasound has a high temporal and spatial resolution, can produce a rich waveform, wide bandwidth of ultrasound, etc., after switching and laser excitation parameter adjustment, the laser ultrasound can be in the parts of any designated part to remove all the tensile stress, in the case of not destroying the integrity of the surface, without heating, the formation of a certain thickness of compressive stress reinforced layer. It is also possible to regulate the stress value to the design requirement range, which can significantly optimize the fatigue and crack resistance of the local position.
