Priming aerospace applications

The applications of glass/glass-ceramic matrix composites (CMC) can be divided into two specific categories aerospace applications and non-aerospace applications. In aerospace applications, performance is the prime consideration, while in non-aerospace applications cost-effectiveness is paramount. The characteristic properties of materials for aerospace applications should be... 

Titanium is widely used in aerospace applications that require high strength-to-weight ratios at elevated temperatures. As a result, a number of different prebonding surface preparation processes have been developed for titanium. These generally follow the same sequence as for steel and other major industrial metal substrates degrease, acid-etch or alkaline-clean, rinse and dry, chemical surface treatment, rinse and dry, and finally prime or bond. Mechanical abrasion is generally not recommended for titanium surfaces. 

In the field of aerospace applications, the reliability of materials under extreme exposure conditions is of prime importance. The high- and low-temperature properties of the fluoroelastomers have permitted them to give reliable performance in a number of aircraft and missile components, specifically manifold gaskets, coated fabrics, firewall seals, heat-shrinkable tubing and fittings for wire and cable, mastic adhesive sealants, protective coatings, and numerous types of O-ring seals. 

The prime reason for accepting the penalties of a lengthened cycle time and the energy cost of heating solvent vapor beyond its normal boiling point is to be able to remove all liquid from parts with complicated stmctures. Two examples are honeycomb panels (with membranes or the ability to cup liquid solvents) used as structural materials for aerospace applications (at lower left), and porous materials which will be used to fabricate implants for humans. 

In aerospace applications, once metallic adherends have been pretreated, it can be several weeks before they are bonded. In view of the fact that most of the oxide or fresh metal surfaces are stable for considerably less than 24 h, these surfaces have to be protected during the time that the component is stored prior to bonding. This is invariably achieved by priming the dried adherend immediately after pretreatment such techniques rarely, if ever, apply to fibre-reinforced composite components. 

Fibers spun from glass are completely inorganic in nature and possess unique properties that cannot be found in organic textile fibers. Glass fibers have some deficiencies in properties that severely limit their use in apparel. Glass fibers are used in a number of industrial and aerospace applications and in selected home furnishing uses where heat and environmental stability are of prime importance. 

Graphite with its exceptional strength and thermal stability at high temperatures is a prime candidate material for many aerospace and nuclear applications. Its properties, through process modifications, are tailorable to meet an array of design criteria for survival under extremely harsh environmental operations. 

Polymers and composites are finding ever-increasing use as structural components in aerospace systems because of their attractive strength/weight characteristics. During the past 20 years, their use in military aircraft has increased from essentially zero in F-4 jets to over 25% in the advanced AV8-B Harrier II. Thermosetting resins, particularly epoxies and polyimides, are of prime interest for use in structural applications. 

Mechanical attachment of components, devices, and other parts of an electronic assembly is the prime function of adhesives. Although adhesives are expected to bond a wide variety of materials for electronic applications, they do not need to be structural. They should, however, meet minimum tensile and shear strengths in order to withstand mechanical shock, thermal shock, thermal cycling, and vibration as specified for the intended application. For consumer and commercial products, these stresses may be minimal. For high reliability aerospace and medical systems, more severe tests as defined in MIL-STD-883 and other documents must be used. 

Today, conventional polymer composites are important commercial materials with a wide range of applications in many industries e.g., aerospace, automotive, etc.) where highly resistant and lightweight materials are of prime importance. In recent years, however, optimizing the properties of the traditional polymer composites containing micrometer-scale reinforcing entities has reached its limits. The micro- and nanosized fibrillar composites open a large window of opportunities to further improve the mechanical prop-... 

Adhesion is fundamentally a surface property. High technologies such as aeronautics, aerospace, electronics and automotive industries are among the prime users of assembly by adhesive bonding. There are also numerous applications in more traditional sectors... 

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