Advanced Composite Materials in the Aviation and Defense Industry

The first powered aircraft heavier than air was built by the Wright brothers in 1903. Aircraft made from canvas fabric and wood, as flight efficiency increased and motor power grew while aircraft weight decreased, created a need for new materials to be used in aircraft. Canvas fabrics were replaced by varnished fabrics, and steel tubes were used where necessary. To elevate lightness to the highest levels in aircraft, aluminum monocoque was used in World War II. These structures and aluminum monocoque are also used today in automobile chassis. For aircraft, however, they are produced from carbon fiber and composite materials, which are easier to shape and light and durable. Weight is at the forefront of the largest problems in the aerospace and defense industries. It is not possible to completely solve this problem, but composite materials are the most suitable material to reduce it. Furthermore, when specific strength and specific stiffness values are considered, composite materials provide superiority over conventional materials due to their low densities in these values. In the early days of modern aircraft design, when material properties and physical laws came together, aircraft lifespans were extended to up to 70 years, and depending on usage frequency, were reduced to and used for up to 40 years according to requirements. Today, nano-component composite materials with new properties have been developed to meet aerospace requirements. Advanced material technologies change in importance between performance and cost depending on sector needs. In military aviation, performance comes before cost. The United States National Aeronautics and Space Administration (NASA) demonstrated in 1987 that despite the high manufacturing cost of composite materials, the total cost is lower due to requiring fewer labor hours.

Role of Fiber-Reinforced Thermoplastics in Aviation

Various composites find application in military transport vehicles and heavy vehicles. One of these composites is continuous fiber-reinforced thermoplastics. Seats, floor panel components, fuselage panels, reinforcement structures, engine covers, wheel wells, railings and fenders in military vehicles represent other parts where composite materials could be utilized to reduce weight. In tail cone design, optimal weight and bending properties are desired. For this reason, the maximum loads the structure may be subjected to are taken into account. Accordingly, composite tail cones are produced with materials and designs capable of meeting the desired loading conditions.

Composite Used in Armor: Kevlar

High strength-to-density ratio, formability, electrical properties, resistance to corrosion and chemical effects, colorability and vibration damping are properties expected from composite materials produced for use in the defense industry. Composite materials are preferred in wing and tail elements of military aircraft such as planes and helicopters, and on takeoff and landing runways, exhaust flaps, armor on tanks, armored vehicles and aircraft, heavy vehicles used in military transport, lightweight body armor, bulletproof vests, gun bodies, liquid armor, unmanned aircraft, bus, truck and other military vehicle seats, and non-flammable military tents. Kevlar is a fiber consisting of very light carbon-based strong fibers, known for being five times stronger than steel of the same weight. It is widely used in the manufacture of bulletproof vests and helmets, vehicle protection, construction of fuselage or wing structures of special vehicles, and vital protection applications such as strategic equipment shields. Composite materials reduce weight in military vehicles while increasing safety. An aircraft fuselage manufactured from 30 mm thick carbon fiber-reinforced composite meets threats as well as a fuselage made from hard steel and is 10% lighter than this steel-made fuselage.

Composite Applications in Military Helicopters

Composite applications in military helicopters, which began in the 1970s, were intended to reduce helicopter weights without compromising durability using composites considered as alternatives to aluminum alloys. In the process to date, since the cost factor carries importance at least equal to performance, both material groups are seen to be used effectively. While 57% by weight of reinforced plastic material, primarily carbon, was used in the construction of the V22 Osprey military helicopter, carbon-epoxy composite was also used in the front section of the fuselage of the NH 90 military transport helicopter. Polymer concrete composite, which provides rapid strength gain, was developed using natural and synthetic resins for military applications in beach and coastal areas. Composite Panel Systems, polymer concrete composite providing rapid strength gain developed by the Advanced Structures and Composites Center at the University of Maine in the USA, was developed using natural and synthetic resins for military applications in beach and coastal areas. These are composite panel systems that can be applied to military tents to protect military personnel from missile and other ballistic threats.

Composite Military Vessels

Manufactured using advanced composite materials for a strong robust structure, the total weight of this vessel is significantly reduced. Reducing weight directly means greater carrying capacity and speed. At the same time, the use of composite materials that improve corrosion resistance reduces periodic maintenance costs. In conclusion, as alternatives to conventional materials, composite materials are widely used in the defense industry due to their high density-to-strength ratio, advanced manufacturing technology, specific strength and high corrosion resistance. With new developments in materials and manufacturing technologies, Turkey is establishing an important position in the defense industry. Prepared by: B. Serhat Cengiz

References Reinforced Plastics, "Moving Into Partnership on Helicopters" (June 2001) Erdem Eryıldız, Ayşegül Akdoğan Eker, "Advanced Composite Materials Used in the Defense Industry and Application Areas" Article, Yıldız Technical University, Department of Mechanical Engineering (2015) https://prezi.com/eljhb4_m6b2t/askeri-ve-savunmasanayinde-kullanilan-kompozit-malzmeler/ https://malzemebilimi.net/havacilik-sanayisinde-kompozit-malzemelerin-yeri.html