洛阳理工学院毕业设计论文
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机械设备一览表
序号 机械设备名称 型号 生产能力（t/h） 数量 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 鄂式破碎机 鄂式破碎机 锤式破碎机 湿式棒磨机 单转式笼磨机 振动筛 六角筛 电子称 QH混合机 QH混合机 皮带输送机 斗式提升机 带式除尘器 双管螺旋给料机 湿式轮碾机 PEF125×250 PEF250×500 PCB600×400 直径1350 Φ2000×900 Φ1100×2 000 TCS QH750 QH375 带速1.00-3.15 D250 合成纤维 1.8 0.45 11.8(m3/h) 17～43.6 t/h 380㎏/盘 6 15 1 1 1-4 5-20 4-15 5.8-12.6 10-20.5 0.1-60 2 2 1 1 1 1 2 9 1 1 50-500㎏ 1.5m宽 备注 ?300?1805 ?1000?350
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洛阳理工学院毕业设计论文
外文资料翻译
Composites in Aerospace Applications
By Adam Quilter, Head of Strength Analysis Group, ESDU International (an IHS company)
Introduction
The aerospace industry and manufacturers‘ unrelenting passion to enhance the performance of commercial and military aircraft is constantly driving the development of improved high performance structural materials. Composite materials are one such class of materials that play a significant role in current and future aerospace components. Composite materials are particularly attractive to aviation and aerospace applications because of their exceptional strength and stiffness-to-density ratios and superior physical properties.
A composite material typically consists of relatively strong, stiff fibres in a tough resin matrix. Wood and bone are natural composite materials: wood consists of cellulose fibres in a lignin matrix and bone consists of hydroxyapatite particles in a collagen matrix. Better known man-made composite materials, used in the aerospace and other industries, are carbon- and glass-fibre-reinforced plastic (CFRP and GFRP respectively) which consist of carbon and glass fibres, both of which are stiff and strong (for their density), but brittle, in a polymer matrix, which is tough but neither particularly stiff nor strong. Very simplistically, by combining materials with complementary properties in this way, a composite material with most or all of the benefits (high strength, stiffness, toughness and low density) is obtained with few or none of the weaknesses of the individual component materials.
CFRP and GFRP are fibrous composite materials; another category of composite materials is particulate composites. Metal matrix composites (MMC) that are currently being developed for the aviation and aerospace industry are examples of particulate composites and consist, usually, of non-metallic
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洛阳理工学院毕业设计论文
particles in a metallic matrix; for instance silicon carbide particles combined with aluminium alloy.
Probably the single most important difference between fibrous and particulate composites, and indeed between fibrous composites and conventional metallic materials, relates to directionality of properties. Particulate composites and conventional metallic materials are isotropic, i.e. their properties (strength, stiffness, etc.) are the same in all directions; fibrous composites are anisotropic, i.e. their properties vary depending on the direction of the load with respect to the orientation of the fibres. Imagine a small sheet of balsa wood: it is much easier to bend (and break) it along a line parallel to the fibres than perpendicular to the fibres. This anisotropy is overcome by stacking layers, each often only fractions of a millimetre thick, on top of one another with the fibres oriented at different angles to form a laminate.
Except in very special cases, the laminate will still be anisotropic, but the variation in properties with respect to direction will be less extreme. In most aerospace applications, this approach is taken a stage further and the differently oriented layers (anything from a very few to several hundred in number) are stacked in a specific sequence to tailor the properties of the laminate to best withstand the loads to which it will be subjected. This way, material, and therefore weight, can be saved, which is a factor of prime importance in the aviation and aerospace industry.
Another advantage of composite materials is that, generally speaking, they can be formed into more complex shapes than their metallic counterparts. This not only reduces the number of parts making up a given component, but also reduces the need for fasteners and joints, the advantages of which are twofold: fasteners and joints may be the weak points of a component — a bolt needs a hole which is a stress concentration and therefore a potential crack-initiation site, and fewer fasteners and joints can mean a shorter assembly time.
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洛阳理工学院毕业设计论文
Shorter assembly times, however , need to be offset against the greater time likely to be needed to fabricate the component in the first place. To produce a composite component, the individual layers, which are often pre-impregnated (?pre-preg‘) 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 composite materials was about 30 years ago when boron reinforced epoxy composite was used for the skins of the empennages of the U.S. F14 and F15 fighters. Initially, composite 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
composite materials are used in the airframe.
Composites in Aerospace Applications
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洛阳理工学院毕业设计论文
Initially, the percentage by structural weight of composites 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 AV-8B Harrier GR7 has composite wing sections and the GR7A features a composite rear fuselage.
Composite materials are used extensively in the Eurofighter: the wing skins, forward fuselage, flaperons and rudder all make use of composites. 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 carbon-fibre-reinforced composite material. Other European fighter typically feature between about 20 and 25 percent composites 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 require-ment for stealth means that radar-absorbing material must be added to the exterior of the air craft with a concomitant weight penalty. Composite materials are therefore used in the primary structure to offset this penalty.
The use of composite materials in commercial transport air-cr aft is attractive because reduced airframe weight enables better fuel economy and therefore lowers operating costs. The first significant use of composite material in a commercial 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 composite fin, lowering its weight and production cost. Later, a honeycomb core with CFRP faceplates was used for the elevator of the A310.Following these successes, composite materials were used for the entire tail structure of the A320, which also featured composite fuselage belly skins, fin/fuselage fairings, fixed leading- and trailing-edge bottom access panels and deflectors, trailing-edge flaps and flap-track fairings, spoilers, ailerons, wheel
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