Bicycle frames

Composites. Various composite materials have evolved over the years as a significant class of high performance textile products. The prototype composite is carbon fiber with an epoxy resin matrix for stmctural akcraft components and other aerospace and military appHcations. Carbon fiber composites ate also used in various leisure and spotting items such as golf clubs, tennis rackets, and lightweight bicycle frames. However, other types of appHcations and composites ate also entering the marketplace. For example, short ceUulose fiber/mbbet composites ate used for hoses, belting, and pneumatic tire components. 

Boron itself has been used for over two decades in filament form in various composites BO3/H2 is reacted at 1300° on the surface of a continuously moving tungsten fibre 12/tm in diameter. US production capacity is about 20 tonnes pa and the price in about 80(. The primary use so far has been in military aircraft and space shuttles, but boron fibre composites are also being studied as reinforcement materials for commercial aircraft. At the domestic level they are finding increasing application in golf shafts, tennis rackets and bicycle frames. 

When given a choice among materials, determining the most energy-wise material seldom easy. Consider the energy needed to build an alnminnm bicycle frame versus a steel tubular frame. The aluminum bicycle frame takes considerably more energy to build, and needs replacement more often. 

Titanium finds uses as diverse as aircraft turbine blades, lightweight bicycle frames, and Ti02 smoke for skywriting. 

Carbon and carbon-glass composites are being used to make advanced-material fishing rods, bicycle frames, golf clubs, baseball bats, racquets, skis and ski poles, basketball back-boards, etc. These come in one color—black—because the carbon fibers are black. Even so, they can be coated with about any color desired. 

Fullerene, black and shiny like graphite, is the subject of active current research because of its interesting electronic properties. When allowed to react with rubidium metal, a superconducting material called rubidium fulleride, Rb3C6o, is formed. (We ll discuss superconductors in more detail in Section 21.6.) Carbon nanotubes are being studied for use as fibers in the structural composites used to make golf clubs, bicycle frames, boats, and airplanes. On a mass basis, nanotubes are up to ten times as strong as steel. 

Fig. 14.3. Construction of a bicycle frame from carbon fiber composite tubing using an Araldite epoxy adhesive. (Courtesy of Huntsman Advanced Materials.)...

Sky boots, boats, bottles, luggage, bicycle frames and accessories... 

Many types of steel contain elements in addition to iron and carbon. Such steels are often called alloy steels and can be viewed as being mixed interstitial (carbon) and substitutional (other metals) alloys. Bicycle frames, for example, are constructed from a wide variety of alloy steels. The compositions of the two brands of steel tubing used in high-quality racing bicycles are given in Table 16.3. 

There are relatively few commercial uses for scandium or its compounds. It is sometimes used to make alloys for special purposes. Scandium metal is lighter than most other metals. It is also resistant to corrosion (rusting) and has a high melting point. These properties make scandium alloys especially desirable for use in sporting equipment, such as baseball bats, lacrosse sticks, and bicycle frames. 

Scandium alloys are used in bicycle frames. lAAAGE COPYRIGHT 2009, SIRKO HARTMANN. USED UNDER LICENSE FROM SHUTTERSTOCK. COM. 

There are two types of alloys. In a substitutional alloy, some of the metal atoms in a crystal lattice are replaced by other atoms (usually of comparable size). Examples are brass, in which approximately one third of the atoms in a copper crystal are replaced by zinc atoms, and pewter, an alloy of tin that contains 7% copper, 6% bismuth, and 2% antimony. In an interstitial alloy, atoms of one or more additional elements enter the interstitial sites of the host metal lattice. An example is steel, in which carbon atoms occupy interstitial sites of an iron crystal, making the material stronger and harder than pure iron. Mild steel contains less than 0.2% C and is used for nails, whereas high-carbon steels can contain up to 1.5% C and are used in specialty applications such as tools and springs. Alloy steels are both substitutional and interstitial atoms from metals such as chromium and vanadium substitute for iron atoms, with carbon remaining in interstitial sites. Alloy steels have a variety of specialized purposes, ranging from cutlery to bicycle frames. 

Titanium is a strong, lightweight, corrosion-resistant metal that is used in rockets, aircraft, jet engines, and bicycle frames. It is prepared by the reaction of titanium(IV) chloride with molten magnesium between 950°C and 1150°C ... 

Aluminum (Al), a metal with a high strength-to-weight ratio and a high resistance to corrosion, is often used for structures such as high-quality bicycle frames. Compufe both the number of moles of atoms and the number of atoms in a 10.0-g sample of aluminum. 

Figure 7.13 Bicycle frames are sometimes made of 3/2.5 titanium alloy, an alloy of titanium containing 3% aluminum and 2.5% vanadium. 

Table 7.13 lists some commercially important alloys and their uses. An alloy of titanium and vanadium is used for the bicycle frame shown in Figure 7.13. Alloys such as this are classified into one of two basic types, substitutional alloys and interstitial alloys. 

The low density of carbon fibre composites compared with metals has resulted in their application as biomaterials. Carbon fibre/epoxy composites are used as plates in bone surgery, replacing the titanium plates previously employed. The combination of high strength and flexibility exhibited by carbon fibre composites has had a huge impact in the performance of sports equipment Fishing rods, golf clubs, bicycle frames, rackets and skis are examples of applications for carbon fibre composites. 

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