【正文】 ssembly times, however , need to be offset against the greater time likely to be needed to fabricate the ponent in the first place. To produce a posite ponent, the individual layers, which are often preimpregnated (‘prepreg’) with the resin matrix, are cut to their required shapes, which are all likely to be different to a greater or lesser extent, and then stacked in the specified sequence over a former (the former is a solid or framed structure used to keep the uncured layers in the required shape prior to, and during, the curing process). This assembly is then subjected to a sequence of temeratures and pressures to‘cure’ the material. The product is then checked thoroughly to ensure both that dimensional tolerances are met and that the curing process has been successful (bubbles or voids in the laminate might have been formed as a result of contamination of the raw materials, for example).The Use of Composites in Aircraft Design Among the first uses of modern posite materials was about 30 years ago when boron reinforced epoxy posite was used for the skins of the empennages of the . F14 and F15 fighters. Initially, posite materials were used only in secondary structures, but as knowledge and development of the materials has improved, their use in primary structures such as wings and fuselages has increased. The following table lists some air craft in which significant amounts of posite materials are used in the airframe.Composites in Aerospace Applications Initially, the percentage by structural weight of posites used in manufacturing was very small, at around two percent in the F15, for example. However, the percentage has gr own considerably, through 19 percent in the F18 up to 24 percent in the F22. The image below, from Reference 1，shows the distribution of materials in the F18E/F aircraft. The AV8B Harrier GR7 has posite wing sections and the GR7A features a posite rear fuselage. Composite materials are used extensively in the Eurofighter: the wing skins, forward fuselage, flaperons and rudder all make use of posites. Toughened epoxy skins constitute about 75 per cent of the exterior area. In total, about 40 percent of the structure al weight of the Eurofighter is carbonfibrereinforced posite material. Other European fighter typically feature between about 20 and 25 percent posites by weight: 26 percent for Dassault’s Rafael and 20 to 25 percent for the Saab Gripen and the EADS Mako. The B2 stealth bomber is an interesting case. The requirement for stealth means that radarabsorbing material must be added to the exterior of the air craft with a conitant weight penalty. Composite materials are therefore used in the primary structure to offset this penalty. The use of posite materials in mercial transport aircr aft is attractive because reduced airframe weight enables better fuel economy and therefore lowers operating costs. The first significant use of posite material in a mercial aircraft was by Airbus in 1983 in the rudder of the A300 and A310, and then in 1985 in the vertical tail fin. In the latter case, the 2,000 parts (excluding fasteners) of the metal fin was reduced to fewer than 100 for the posite fin, lowering its weight and production cost. Later, a honeyb core with CFRP faceplates was used for the elevator of the these successes, posite materials were used for the entire tail structure of the A320, which also featured posite fuselage belly skins, fin/fuselage fairings, fixed leading and trailingedge bottom access panels and deflectors, trailingedge flaps and flaptrack fairings, spoilers, ailerons, wheel doors, main gear leg fairing doors, and nacelles. In addition, the floor panels were made of GFRP. In total, posites constitute 28 per cent of the weight of the A320 airframe. The A340500 and 600 feature additional posite structures, including the rear pressure bulkhead, the keel beam, and some of the fixed leading edge of the wing. The last is particularly significant, as it constitutes the first largescale use of a thermoplastic matrix posite ponent on a mercial transport aircraft. Composites enabled a 20 percent saving in weight along with a lower production time and improved damage tolerance. The A380 is about 2022 percent posites by weight and also makes extensive use of GLARE (glassfibrereinforced aluminium alloy), which features in the front fairing, upper fuselage shells, crown and side panels, and the upper sections of the forward and aft upper fuselage. GLARE laminates are made up of four or more mm ( in) thick sheets of aluminium allo y and glass fibre resin bond film. GLARE offers weight savings of between 15 and 30 percent over aluminium alloy along with very good fatigue resistance. The top and bottom skin panels of the A380 and the front, centre and rear spars contain CFRP, which is also used for the rear pressure bulkhead, the upper deck floor beams, and for the ailerons, spoilers and outer flaps. The belly fairing consists of about 100 posite honeyb panels. The Boeing 777, whose maiden flight was 10 ten years ago, is around 20 percent posites by weight, with posite materials being used for the wing’s fixed leading edge, the trailingedge panels, the flaps and flaperons, the spoilers, and the outboard aileron. They are also used for the floor beams, the wingtobody fairing, and the landinggear doors. Using posite materials for the empennage saves approximately 1,500 lb in weight.Composites in Aerospace ApplicationsThe Boeing 7E7 will leverage extensive use of posite materials (estimates are as high as 50 percent) in the quest for very high efficiency and performance with reduced weight. The excellent strengthtoweight ratio of posites is also used in helicopters to maximize payloads and performance in general. Boeing Vertol used posites for rotorcraft fairings in the 1950s and made the first posite rotor blades in the 1970s. Composites are used in major structural elements of many m