A crack arrestor (otherwise known as a rip-stop doubler) is a structural

engineering Engineering is the use of scientific method, scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad rang ...

device. Being typically shaped into ring or strip, and composed of a strong material, it serves to contain

stress corrosion cracking Stress corrosion cracking (SCC) is the growth of crack formation in a corrosive environment. It can lead to unexpected and sudden failure of normally ductile metal alloys subjected to a tensile stress, especially at elevated temperature. SCC ...

fatigue Fatigue describes a state of tiredness that does not resolve with rest or sleep. In general usage, fatigue is synonymous with extreme tiredness or exhaustion that normally follows prolonged physical or mental activity. When it does not resolve ...

cracking, helping to prevent the catastrophic failure of a device. The crack arrestor can be as simple as a thickened region of metal, or may be constructed of a

laminated Lamination is the technique/process of manufacturing a material in multiple layers, so that the composite material achieves improved strength, stability, sound insulation, appearance, or other properties from the use of the differing material ...

woven Woven fabric is any textile formed by weaving. Woven fabrics are often created on a loom, and made of many threads woven on a warp and a weft. Technically, a woven fabric is any fabric made by interlacing two or more threads at right angles to o ...

material that can be designed to withstand deformation without failure. When correctly applied, the technique is capable of redirecting movement and safely distributing stresses. The crack arrestor is considered to be compatible with

fail-safe In engineering, a fail-safe is a design feature or practice that in the event of a specific type of failure, inherently responds in a way that will cause minimal or no harm to other equipment, to the environment or to people. Unlike inherent safe ...

design practices.

Applications

Crack arrestors have seen extensive use in the aviation sector, particularly upon large pressurised aircraft as a means of guarding against progressive metal fatigue. Specifically, the skin of the fuselage typically has a large number of high stress locations,

rivet A rivet is a permanent mechanical fastener. Before being installed, a rivet consists of a smooth cylindrical shaft with a head on one end. The end opposite to the head is called the ''tail''. On installation, the rivet is placed in a punched ...

ting being a leading cause, making these points of potential crack initiation. Calculations are frequently used to simulate crack propagation, as well as the effectiveness of mitigating measures, such as crack arrestors, in ensuring the aircraft can be safely operated. Following two catastrophic airframe failures in 1954, crack arrestors were used as additional reinforcement of the fuselage of the

de Havilland Comet The de Havilland DH.106 Comet was the world's first commercial jet airliner. Developed and manufactured by de Havilland in the United Kingdom, the Comet 1 prototype first flew in 1949. It featured an aerodynamically clean design with four ...

, although this was only one of several design changes made to address structural design weaknesses related to

metal fatigue In materials science, fatigue is the initiation and propagation of cracks in a material due to cyclic loading. Once a fatigue crack has initiated, it grows a small amount with each loading cycle, typically producing striations on some parts o ...

and skin stresses that had been previously unknown to the aviation industry. Naval vessels are another place where crack arrestors have been extensively used. As of the 2010s, the

United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...

frequently applies them to areas of the ship that have been damaged or otherwise have received repairs in order to ensure that the affected element is not lacking in either strength or durability. It has been acknowledged that ships primarily composed of

aluminium Aluminium (aluminum in AmE, American and CanE, Canadian English) is a chemical element with the Symbol (chemistry), symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately o ...

are significantly more prone to crack propagation than older steel counterparts; thus, the use of mitigating measures is likely to become more commonplace. Crack arrestors have also been used in

civil engineering Civil engineering is a professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including public works such as roads, bridges, canals, dams, airports, sewa ...

. They have long been used in the

nuclear Nuclear may refer to: Physics Relating to the nucleus of the atom: *Nuclear engineering *Nuclear physics *Nuclear power *Nuclear reactor *Nuclear weapon *Nuclear medicine *Radiation therapy *Nuclear warfare Mathematics *Nuclear space * Nuclear ...

industry as a structural element of reactors. Numerous pipelines used from transporting chemicals have been reinforced with such devices to protect against bursting and exterior damage alike. While commonly applied to metal alloys, appropriately designed crack arrestors have been used with composite materials as well. During 2008,

Airbus Group Airbus SE (; ; ; ) is a European multinational aerospace corporation. Airbus designs, manufactures and sells civil and military aerospace products worldwide and manufactures aircraft throughout the world. The company has three divisions: '' ...

was awarded a

patent A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an sufficiency of disclosure, enabling disclo ...

for a new design technique for a crack arrestor component.

Citations

Fracture mechanics Aircraft components Aerospace engineering {{Engineering-stub