Share | 


Go down 

Jumlah posting : 86
Join date : 06.05.10

PostSubyek: BAHAN DASAR PEMBUATAN WAHANA SILUMAN.   Wed May 26, 2010 3:37 am


Powder of carbon nanotubes

Carbon nanotubes (CNTs; also known as buckytubes) are allotropes of carbon with a cylindrical nanostructure. Nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000:1,[1] which is significantly larger than any other material. These cylindrical carbon molecules have novel properties that make them potentially useful in many applications in nanotechnology, electronics, optics and other fields of materials science, as well as potential uses in architectural fields. They exhibit extraordinary strength and unique electrical properties, and are efficient thermal conductors.

Nanotubes are members of the fullerene structural family, which also includes the spherical buckyballs. The ends of a nanotube might be capped with a hemisphere of the buckyball structure. Their name is derived from their size, since the diameter of a nanotube is on the order of a few nanometers (approximately 1/50,000th of the width of a human hair), while they can be up to 18 centimeters in length (as of 2010).[1] Nanotubes are categorized as single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs).

From Ultrasonic Cavitation disperses Multiwall Nanotubes (hydrophobic) in Water.

The nature of the bonding of a nanotube is described by applied quantum chemistry, specifically, orbital hybridization. The chemical bonding of nanotubes is composed entirely of sp2 bonds, similar to those of graphite. This bonding structure, which is stronger than the sp3 bonds found in diamonds, provides the molecules with their unique strength. Nanotubes naturally align themselves into "ropes" held together.

Application for stealth.

The H-8 bomber was a Chinese military aircraft that was a possible successor to the Xian H-6 twin-engine jet bomber. The prototype aircraft was reported to be an enlarged version of the H-6 with underwing engines, but that the project was canceled in the early 1970s before the bomber went into production. the China military has a stealth bomber called Xian H-8. The bomber has 4 Ws-10A engines derived from Russian and US technology. It is made from carbon fiber and coated with special nanotechnology. well, the Xian H-8 has a max speed of Mach 1.2 and carries stealth missiles in its cargo bay. The bomber also can carry nuclear missiles. China is currently developing stealth fighters like J-XX and J-13 (which is based on the J-10).

It is the world’s second Stealth bomber, and is more advanced than the American B-2. Because the project is top-secret, little is known about the aircraft. It is a Stealth, strategic, and heavy bomber rolled into one. It carries a crew of two. It could fly as fast as Mach 1.4, has a range of 11,000 kilometers (without refuelling), and can carry over 18 tonnes of bomb load. It can carry twelve Stealth cruise missiles (each with a range of 3,000 km) on each of the two weapons bays. It could carry an additional three nuclear missiles (350-kilotons each). The bomber will be mass-produced and will enter active service in the PLAAF by 2010. The bomber will replace the old H-6 bombers that the PLAAF have in active service.

Here are only SOME of the features:
-high-tech blended wing-body design
-fly-by-wire controls
-angled fuselage
-internal fuel tanks.
-carbon fiber and composite materials
-rotating weapons profile bay
-mapping radar, satellite data links and advanced digital mapping systems
-nanometer coating
-4 turbo-fan engines - based on the WS-10A

Fabric made of woven carbon filaments.

Carbon fiber (carbon fibre), alternatively graphite fiber, carbon graphite or CF, is a material consisting of extremely thin fibers about 0.005–0.010 mm in diameter and composed mostly of carbon atoms. The carbon atoms are bonded together in microscopic crystals that are more or less aligned parallel to the long axis of the fiber. The crystal alignment makes the fiber very strong for its size. Several thousand carbon fibers are twisted together to form a yarn, which may be used by itself or woven into a fabric.[1] Carbon fiber has many different weave patterns and can be combined with a plastic resin and wound or molded to form composite materials such as carbon fiber reinforced plastic (also referenced as carbon fiber) to provide a high strength-to-weight ratio material. The density of carbon fiber is also considerably lower than the density of steel, making it ideal for applications requiring low weight.[2] The properties of carbon fiber such as high tensile strength, low weight, and low thermal expansion make it very popular in aerospace, civil engineering, military, and motorsports, along with other competition sports. However, it is relatively expensive when compared to similar materials such as fiberglass or plastic. Carbon fiber is very strong when stretched or bent, but weak when compressed or exposed to high shock (eg. a carbon fiber bar is extremely difficult to bend, but will crack easily if hit with a hammer).

A 6 μm diameter carbon filament (running from bottom left to top right) compared to a human hair.

Structure and properties
Carbon fibers are the closest to asbestos in a number of properties.[4] Each carbon filament thread is a bundle of many thousand carbon filaments. A single such filament is a thin tube with a diameter of 5–8 micrometers and consists almost exclusively of carbon. The earliest generation of carbon fibers (i.e., T300, and AS4) had diameters of 7-8 micrometers[5]. Later fibers (i.e., IM6) have diameters that are approximately 5 micrometers[5].

The atomic structure of carbon fiber is similar to that of graphite, consisting of sheets of carbon atoms (graphene sheets) arranged in a regular hexagonal pattern. The difference lies in the way these sheets interlock. Graphite is a crystalline material in which the sheets are stacked parallel to one another in regular fashion. The intermolecular forces between the sheets are relatively weak Van der Waals forces, giving graphite its soft and brittle characteristics. Depending upon the precursor to make the fiber, carbon fiber may be turbostratic or graphitic, or have a hybrid structure with both graphitic and turbostratic parts present. In turbostratic carbon fiber the sheets of carbon atoms are haphazardly folded, or crumpled, together. Carbon fibers derived from Polyacrylonitrile (PAN) are turbostratic, whereas carbon fibers derived from mesophase pitch are graphitic after heat treatment at temperatures exceeding 2200 C. Turbostratic carbon fibers tend to have high tensile strength, whereas heat-treated mesophase-pitch-derived carbon fibers have high Young's modulus and high thermal conductivity.

Carbon fiber is most notably used to reinforce composite materials, particularly the class of materials known as Carbon fiber or graphite reinforced polymers. Non-polymer materials can also be used as the matrix for carbon fibers. Due to the formation of metal carbides and corrosion considerations, carbon has seen limited success in metal matrix composite applications. Reinforced carbon-carbon (RCC) consists of carbon fiber-reinforced graphite, and is used structurally in high-temperature applications. The fiber also finds use in filtration of high-temperature gasses, as an electrode with high surface area and impeccable corrosion resistance, and as an anti-static component. Molding a thin layer of carbon fibers significantly improves fire resistance of polymers or thermoset composites because a dense, compact layer of carbon fibers efficiently reflects heat.

New JASDF Stealth Fighter Jet to be "Made In Japan"

Not your grandfather's Mitsubishi...

"Son of Zero", resplendent in carbon fiber

It has also been used in experimental medical procedures to treat severe burns. Brian Eno underwent extensive surgery in early 2009 which complemented a regular skin graft on his arm with carbon fiber threads. Being carbon based, doctors were able to fuse together his skin cells with the carbon fiber.

Most recently, carbon fiber composites have been used in Helios braces, braces for persons with Charcot-Marie-Tooth disease and other Peripheral neuropathy disorders.

The Navy’s Carbon Fiber Composite Stealth Warship.

In the past, the U.S. Navy has lagged behind the other branches of the military in large scale use of advanced carbon fiber composites in essential combat hardware. More specifically, its ships but this is about to change with the building of the first of a new family of advanced, multi-mission destroyers, the DDG-1000 Zumwalt class.

The challenge for the Navy is to meet fire-retardant/fire containment requirements, while reducing radar signature and weight, and yet control cost during construction of four upper decks of the destroyer’s deck house superstructure. To rise to this challance the Navy will use primarily flat carbon composite sandwich panels to simplify tooling, and core them with balsa, which burns more slowly than foam and better insulates the opposite sandwich skin from heat, optimizing fire safety.
The Zumwalt class had its begining in 2001, when the Navy announced the program would move forward after the DD 21 project. The goal is to release 32 new multi-mission destroyers by 2012. The Navy renamed it DDG-1000 and shrank it to three ships in 2008, although the DD plan originally called for 8 to 12 “advanced technology surface combatants,”. The new ships were to provide support for land attack and ground forces, unlike traditional destroyers, which primarily engage in offshore anti-air and undersea warfare.

The ship design includes an upper-section deck house (superstructure) constructed with panels and beams made of carbon fiber/vinyl ester skins with balsa wood and/or foam cores. The ship also features a composite helicopter hanger built of carbon composites, as well as a built in advanced composite ballistic screen. The composite deck house for the first ship (the Zumwalt) is in progress at Northrop Grumman’s shipbuilding facility in Gulfport, Mississippi, under the supervision of the Zumwalt’s main general contractor, General Dynamics based out of Maine.

The Navy first looked into expanding the use of advanced carbon fiber composites in its large capital ships fleet, just over 15 years ago. Glass fiber-reinforced polymers had been used but only in the construction of small river patrol boats, minesweepers and for various small components and hardware on the larger ships. The first large-scale application involved the USS San Antonio (LPD 17) and set the stage for the use of advanced composites in the DDG-1000 program.

Zumwalt has a “tumblehome” hull shape. Which is a design in which the hull slopes inward from above the waterline. This is because the ships will handle tactical landing operations, stealth has been a major consideration in the ship’s design. Such a shape drastically reduces the ship’s radar cross section. Official Naval Technology documentation describes the deck house as “fully EMC shielded with reduced infrared and radar signatures.” The all-composite dech house superstructure has helped the Navy fulfill its goals, as well as reduce top heavy weight and total ship weight.

The DDG-1000 project evaluated a ridiculous number of material combinations, generating more than 6,000 individual test pieces over 10 years. Ultimately, the engineering team settled on a sandwich construction, featuring balsa supplied from New Jersey, between skins made from Toray T700 12K carbon fiber, supplied by Toray Carbon Fiber America Inc of Texas, and the 510A vinyl ester resin from Ohio. Then a California based company wove the T700 fiber into three different types of fabric: a noncrimp ±45° stitched material at a weight of 410 g/m², a bonded unidirectional material at 680 g/m², and a plain-weave 0°/90° fabric at 300 g/m².

The T700 fiber was chosen because it provided us with the required stiffness in whatever fabric we selected it in,” said Barry Heaps (project director). Navy engineers selected balsa core because they learned early in their testing of composite materials that “the mechanical properties of balsa as a core material compared to its cost are significantly better than any other material.” Navy tests also showed that a balsa-core sandwich contained fires better than those cored with foam or honeycomb.

For the most part, the composite panels are flat, an outcome dictated by a desire to keep down tooling costs. Tooling is typically coated with a release agent prior to the layup of the external reinforcing fabrics, balsa core and interior fabrics. A woven glass cloth peel ply also is usually placed on the tool or external side of the panel. The cloth is peeled off after infusion and cure, providing a clean, bondable surface for secondary bonding and assembly. A stainless steel mesh also is integrated into the fabric on the external skin, providing electromagnetic interference (EMI) shielding and a lightning ground in the otherwise nonconductive panels.

The unidirectional fabric is used in areas and structures where higher stiffness is needed in one single direction. “We have some very large beams that support a large open area in the helicopter hanger and those beams are made with the unidirectional material,” said Heaps, telling that the heavier material is significantly more difficult to infuse with the resins.

Although vacuum assisted resin transfer molding (VARTM) is exclusively used for the sandwiched panels on the Zumwalt, Heaps said the team is considering some pultruded sandwich panels in the construction of the second DDG-1000 ship. “Pultrusion has the potential to be cheaper, but there’s still some testing and work to be done to implement them in a deck house,” via HPC via NGSB.

Kembali Ke Atas Go down
Lihat profil user
Kembali Ke Atas 
Halaman 1 dari 1

Permissions in this forum:Anda tidak dapat menjawab topik