Aerospace

Aerospace uses a large number of plastic components, most of which contain fillers for various reasons. It is difficult to follow the development in these components 

In another, relatively new, development, a high purity thermal carbon black was used as a component of an adhesive lining used in the construction of solid-fuel rocket motors and space shuttle motors. 

Aerospace [1] was one of the earliest target application areas for PAEK. In part this was because the industry is relatively insensitive to material costs - especially if reduced component weight results in fuel savings. It was also driven by the interest in thermoplastic composites for high-performance military aircraft. Both HTX and ITX (see Chapter 1) were developed as matrix resins for military aircraft composites. 

Over the years PAEK have progressively replaced metal components, traditional composites and plastics in aircraft. This has been driven by ease of fabrication, weight, mechanical properties, and resistance to jet fuels, hydraulic fluids and rain erosion together with Are smoke and toxicity performance. 

The limited ultraviolet (UV) resistance of PAEK has not ruled out all exterior applications. Fillers and coatings can be used to reduce 

Inside aircraft the fire, smoke and toxicity performance of PAEK is often their key advantage versus other plastics. PAEK produce relatively little smoke and toxic gas in fire situations and they are used extensively in cabin structures. Polyaryletherketoneketone (PEKK) (often laminated with Tedlar) is used to make thermoformed cabin interior panels. Amorphous PEKK has the advantage of being thermoformable at relatively low temperatures which are compatible with polyvinylidene fluoride (PVDF) and the various adhesives used in the laminate. PEEK is found in window surrounds, passenger service units and lamp housings. Glass fibre-reinforced PEEK is used in the 

PEEK finds uses in unmanned aerial vehicles. The Allied Aerospace electric micro aerial vehicle uses PEEK because of its environmental resistance, low weight, mechanical properties and ease of fabrication 

The endurance benefits and performance characteristics of polyamide-imides qualify them to be an excellent replacement for metal in aerospace components. Inherent nonflammability, chemical resistance, and superb strength at elevated temperatures allow polyamide-imide compounds to be used in metal applications once unheard of for plastic materials. Neat resin, friction and wear, along with glass- and carbon-reinforced polyamide-imide compounds are incorporated in a variety of parts and locations in aerospace vehicles. 

Aerospace composite adhesives. In addition to molded parts, polyamide-imides are used as the high-strength adhesives and polymer matrix in aerospace composites. One particular area is honeycomb composites [19]. The adhesives and polymer matrix are critical because the ultimate strength of the honeycomb is often directly dependent on the strength of the bond between the honeycomb layers. The polyamide-imide resin is dissolved in an appropriate solvent and applied to the honeycomb fabric, using a bonding technique to achieve the desired 

The final composite structures claim excellent chemical resistance, high strength, moderate ductility, and toughness. 

Engine components. Parts fabricated from injection-molded fiber-reinforced polyamide-imides provide a lower-cost solution to previously machined metal pieces and maintain, due to low shrinkage, very tight tolerances which are required in these applications. Polyamide-imide compounds have replaced expensive titanium in air return grills for commercial aircraft engines (Fig. 12.13). The shroud on the interior of the aircraft engine, responsible for directing airflow, consists of an assembly of multiple polyamide-imide injection-molded pieces (Fig. 12.14). 

Metal aircraft parts are easily converted to parts composed of polyamide-imide, because of the metal-like coefficient of thermal expansion of the filled compounds. The high modulus and low creep of polyamide-imides provide outstanding thread-holding ability for nonmetallic and thermally-isolating aerospace fastener mounts [20]. 

During the last half-century, aeronautics technology has soared, with plastics playing a major role. Lightweight durable plastics and reinforced plastics (RPs) save on fuel while standing up to forms of stress like creep and fatigue, in different environments. 

Materials used in external parts of an aircraft are exposed to very demanding conditions such as veiy low pressure, a large temperature variation within a short period of time, a large amount of stress, UV, an influence of aggressive chemical liquids. Materials used in spacecraft are exposed to still higher temperature changes, intensity of UV radiation, 

It has often been observed that the application of adhesives to metal fabrication, in common with many other technological innovations, was pioneered by the aircraft industry. It is ironic that this industry, in which safety and reliability command paramount attention, should lead the departure from traditional methods of joining. Today adhesives are used to bond critical parts in commercial and military aircraft and helicopters, spacecraft, rockets, missiles and the US Space Shuttle. The American Primary Adhesively Bonded Structure Technology (PABST) Programme, which ran from 1976-81, was an imaginative attempt to advance significantly the use of bonded 

Nitrile phenolic Bonding metal honeycombs and skins for high-temperature situations 

Adhesives are used as two-component liquids and pastes, one-component heat-cured liquids and pastes (often two-component systems that have been pre-mixed and frozen for storage), films and pressure sensitives. Because of the emphasis on light weight in aircraft. 

Panels for exterior and interior use are fabricated from aluminium in a sandwich-type structure using a honeycomb core with panel skins. This gives a combination of very high strength and low weight. Aluminium or materials like aramid can be used to construct the honeycomb cores. 

Heat-curable epoxy paste and film adhesives are used to bond the honeycomb and to bond skins to honeycombs. Nitrile phenolics are often used for high-temperature applications 240 °C where they show better strength retention than epoxies. The adhesives are cured in heated presses. 

Adhesive sealants are applied throughout the aircraft primarily to seal-out moisture and contaminants. This helps prevent corrosion, particularly on faying (i.e., closely or tightly fitting) surfaces, inside holes and slots, and around installed fasteners. Sealants are also used to seal fuel tanks and pressurised components. They are applied using tubes, spatulas, brushes, rollers, or spray guns. Sealants are often stored frozen and thawed before use, and many are two-component mixtures that cure after mixing. 

---

Recently ultrasonic spectroscopy has become a more common NDE technique and specialized instruments are commercially available now for inspection of aerospace structures, ball bearings, and even concrete [2],[3]. 

The performance of the classifier has been verified using a number of practical applications, such as civil engineering [3], inspection of aerospace composite structures, ball bearings and aircraft multi-layer structures. Here we present shortly some results, focusing on detection of disbonds in adhesively joint multi-layer aerospace structures using Fokker Bond Tester resonance instrument, details can be found in [1]. 

Aerospace struetwes made of composite. As part of the evaluation of the developed ultrasonic spectroscopy system the NSC software was tested on ultrasonic resonance spectra from composite panel samples. Spectra were collected with four different types of damages, and from flawless samples. The damages included a small cut in one of the carbon fiber... 

We have presented a neural network based spectrum classifier (NSC) aimed at ultrasonic resonance spectroscopy. The ultrasonic spectroscopy and the NSC has been evaluated in many industrial applications, such as concrete inspection, testing of aerospace composite structures, ball bearings, and aircraft multi-layer structures. The latter application has been presented in some detail. 

Eddy-current non-destructive evaluation is widely used in the aerospace and nuclear power industries for the detection and characterisation of defects in metal components. The ability to predict the probe response to various types of defect is highly valuable since it enables the influence of particular parameters to be studied without recourse to costly and time consuming experiments. The solution of forward problems is also essential in the process of inverting experimental data. 

The case of thin-skin regime appears in various industrial sectors such as aerospace (with aluminium parts) and also nuclear in tubes (with ferromagnetic parts or mild steel components). The detection of deeper defects depends of course on the choice of the frequency and the dimension of the probe. Modelling can evaluate different solutions for a type of testing in order to help to choose the best NDT system. 

In the intervening years mueh excellent analytical work has been done by Libby, Lord, Dodd, Deeds, Palanisamy and many others which has given us a practical method of understanding eddy current behavior in many applications including nuclear inspection and aerospace where problems of safety and reliability have become so important to us all. 

In wide sectors of industry there is a growing need of inspection methods which go without liquid coupling media. The excitation of bulk and surface waves by means of air-coupled ultrasonic probes is therefore an attractive tool for NDE. This is tme e.g. for the rapid scanning of large composite structures in the aerospace industry [1]. In other cases, the use of liquid couplants is prohibitive like the thickness measurement of powder layers. 

BE-6021 Development of an understanding of materials properties under the combined influence of creeo. fatioue and oxidation. Mr. G. Koenig Daimler-Benz Aerospace... 

BE-1924 Monitoring On-line integrated technologies for operational reliability Mr. P. Hodgkinson British Aerospace Ltd... 

The Zaporozhje Motor-Sich plant manufactures aircraft engines for all the CIS countries. One of the world largest aerospace concerns - Pivdenny - is functioning in Dniepropetrovsk Kharkov turbines are known in many countries. A high-capacity chemical production complex is located in the city of Kaloush. 

Stale of the art, 8 chapters inch 60 Fig.. Months with special focus on TOFD, Thickness Gauging, Aerospace, Power Generation... 

It also has lubricating properties similar to graphite. The hydrides are easily oxidized with considerable energy liberation, and have been studied for use as rocket fuels. Demand is increasing for boron filaments, a high-strength, lightweight material chiefly employed for advanced aerospace structures. 

Aerospace industry Aerospace structures Aerotex Antistatic D... 

The practice of employing reusable thermal protection systems for reentry is becoming more common. These are essentially ablative materials exposed to environments where veryHtde ablation actually occurs. Examples iuclude the space shuttle tiles and leading edges, exhaust no22le flaps for advanced engines, and the proposed stmctural surface skin for the National Aerospace plane. 

Other forms of carbon-carbon composites have been or are being developed for space shutde leading edges, nuclear fuel containers for sateUites, aircraft engine adjustable exhaust nozzles, and the main stmcture for the proposed National Aerospace plane (34). For reusable appHcations, a siHcon carbide [409-21 -2] based coating is added to retard oxidation (35,36), with a boron [7440-42-8] h Lsed sublayer to seal any cracks that may form in the coating. 

Cera.micA.bla.tors, Several types of subliming or melting ceramic ablators have been used or considered for use in dielectric appHcations particularly with quartz or boron nitride [10043-11 -5] fiber reinforcements to form a nonconductive char. Fused siHca is available in both nonporous (optically transparent) and porous (sHp cast) forms. Ford Aerospace manufactures a 3D siHca-fiber-reinforced composite densified with coUoidal siHca (37). The material, designated AS-3DX, demonstrates improved mechanical toughness compared to monolithic ceramics. Other dielectric ceramic composites have been used with performance improvements over monolithic ceramics (see COMPOSITE MATERIALS, CERAMIC MATRIX). 

Bisphenol A. One mole of acetone condenses with two moles of phenol to form bisphenol A [80-05-07] which is used mainly in the production of polycarbonate and epoxy resins. Polycarbonates (qv) are high strength plastics used widely in automotive appHcations and appHances, multilayer containers, and housing appHcations. Epoxy resins (qv) are used in fiber-reinforced larninates, for encapsulating electronic components, and in advanced composites for aircraft—aerospace and automotive appHcations. Bisphenol A is also used for the production of corrosion- and chemical-resistant polyester resins, polysulfone resins, polyetherimide resins, and polyarylate resins. 

The principal type of shear test specimen used in the industry, the lap shear specimen, is 2.54 cm wide and has a 3.23-cm overlap bonded by the adhesive. Adherends are chosen according to the industry aluminum for aerospace, steel for automotive, and wood for constmction appHcations. Adhesive joints made in this fashion are tested to failure in a tensile testing machine. The temperature of test, as weU as the rate of extension, are specified. Results are presented in units of pressure, where the area of the adhesive bond is considered to be the area over which the force is appHed. Although the 3.23-cm ... 

Epoxy stmctural adhesives are used in an extraordinarily wide range of appHcations. They are available in essentially all of the forms discussed above, except for primer—Hquid combinations or as room temperature curing Hquids. The highest technology appHcation for epoxies is in aerospace stmctural... 

Phenohc resins are the oldest form of synthetic stmctural adhesives. Usage ranges from bonding automobile and other types of brake linings to aerospace apphcations. These adhesives have a reputation for providing the most durable stmctural bonds to aluminum. Because of volatiles, however, and the need for high pressures, the phenohc resins are used less as adhesives than the epoxy resins. 

S. A. Moses, "Explosive Components for Aerospace Systems," in Behaviour and Utilisation ofiExplosives in Engineering Design,... 

J. A. Stein, P. L. Stang, and M. Summerfield, The Burning Mechanism ofMmmonium Perchlorate-Based Composite Propellants, Aerospace and Mechanical Sciences Report 830, Princeton University, N.J., 1969. 

T. L. Boggs and R. L. Derr, eds., Ha ard Studiesfor Solid Propellant Pocket Motors, NATO Advisory Group for Aerospace Research and Development, Agardograph 316, Technical Press, London, Sept. 1990. 

W. P. Killian, "Loading Composite Sohd Propellant Rockets—Cuiient Technology," Proceedings Symposium on Selected Topics in Aerospace Chemistry, 64th National Meeting AlCE, Odando, Fla., 1968. 

G. L. Coppoc and S. J. Leger, "Effect of Nitrogen Triduoride on Plasma Concentrations of Lactate, Methemoglobin, and Selected Enzymes," ApriWune 1968, SAM-TR-70-42 (AD 711044), School of Aerospace Medicine, Brooks Air Eorce Base, Texas, July 1970. 

Electrical Applications. The largest application of PTFE is for hookup and hookup-type wire used in electronic equipment in the military and aerospace industries. Coaxial cables, the second largest appHcation, use tapes made from fine powder resins and some from granular resin. Interconnecting wire appHcations include airframes. Other electrical appHcations include computer wire, electrical tape, electrical components, and spaghetti tubing. 

Fiber-reiaforced panels covered with PVF have been used for greenhouses. Transparent PVF film is used as the cover for flat-plate solar collectors (114) and photovoltaic cells (qv) (115). White PVF pigmented film is used as the bottom surface of photovoltaic cells. Nonadhering film is used as a release sheet ia plastics processiag, particularly ia high temperature pressing of epoxy resias for circuit boards (116—118) and aerospace parts. Dispersions of PVF are coated on the exterior of steel hydrauHc brake tubes and fuel lines for corrosion protection. 

Gels. Fluorosihcone fluids with vinyl functionahty can be cured using the platinum catalyst addition reactions. The cure can be controlled such that a gel or a soft, clear, jelly-like form is achieved. Gels with low (12% after 7 d) swell in gasoline fuel are useflil (9) to protect electronics or circuitry from dust, dirt, fuels, and solvents in both hot (up to 150°C) and cold (down to —65° C) environments. Apphcations include automotive, aerospace, and electronic industries, where harsh fuel—solvent conditions exist while performance requirements remain high. 

---