BY JACK AND TABO FIBER REINFORCED COMPOSITE

BY JACK AND TABO FIBER REINFORCED COMPOSITE

DEFINITION: FIBRE-REINFORCED PLASTIC (FRP) (ALSO FIBRE- REINFORCED POLYMER) IS A COMPOSITE MATERIAL MADE OF A POLYMER MATRIX REINFORCED WITH FIBRES. THE FIBRES ARE USUALLY GLASS, CARBON, ARAMID, OR BASALT. RARELY, OTHER FIBRES SUCH AS PAPER OR WOOD OR ASBESTOS HAVE BEEN USED.

DIFFERENT TYPES: Single layered composites. Multi layered composites. Single layered fibers are either continuous fibers or discontinuous fibers. Multi layered fibers are either Laminates and Hybrids.

DIFFERENT TYPES: Continuous fibers are either unidirectional or bidirectional. Discontinuous fibers are either Random orientation or Preffered orientation. Composite materials are formed by combining a reinforcing material such as wood pulp, and a bonding agent, such as glue. The wood pulp is made from the waste from cutting solid wood. MDF and GRP are examples of composite materials.

KEVLAR BONDS: STRUCTURE OF KEVLAR: Kevlar is a very strong artificial fibre. It is woven to make a material that is used for light and flexible body armour. Kevlar is basically a super strong plastic It is strong and tough because: Its molecules can pack closely together There are chemical bonds between adjacent molecules

ADVANTAGES: It's strong but relatively light. The specific tensile strength (stretching or pulling strength) of both Kevlar 29 and Kevlar 49 is over eight times greater than that of steel wire. Unlike most plastics it does not melt: it's reasonably good at withstanding temperatures and decomposes only at about 450 C (850 F). Unlike its sister material, Nomex, Kevlar can be ignited but burning usually stops when the heat source is removed. Very low temperatures have no effect on Kevlar: DuPont found "no embrittlement or degradation" down to 196 C ( 320 F). Like other plastics, long exposure to ultraviolet light (in sunlight, for example) causes discoloration and some degradation of the fibers in Kevlar. Kevlar can resist attacks from many different chemicals, though long exposure to strong acids or bases will degrade it over time. In DuPont's tests, Kevlar remained "virtually unchanged" after exposure to hot water for more than 200 days and its super-strong properties are "virtually unaffected" by moisture.

DISADVANTAGES: It's worth noting that Kevlar also has its drawbacks. In particular, although it has very high tensile (pulling) strength, it has very poor compressive strength (resistance to squashing or squeezing). That's why Kevlar isn't used instead of steel as a primary building material in things like buildings, bridges, and other structures where compressive forces are common.

MANUFACTURING PROCESS: There are two main stages involved in making Kevlar. First you have to produce the basic plastic from which Kevlar is made (a chemical called polypara-phenylene terephthalamide). Polyamides like Kevlar are polymers (huge molecules made of many identical parts joined together in long chains) made by repeating amides over and over again. Amides are simply chemical compounds in which part of an organic (carbon-based) acid replaces one of the hydrogen atoms in ammonia (NH3). So the basic way of making a polyamide is to take an ammonia-like chemical and react it with an organic acid. This is an example of what chemists call a condensation reaction because two substances fuse together into one.

CARBON FIBER: STRUCTURE OF CARBON FIBER: Carbon fiber was first invented near Cleveland, Ohio, in 1958. It wasn t until a new manufacturing process was developed at a British research center in 1963 that carbon fiber's strength potential was realized. Carbon fiber can be woven into a fabric that is suitable for use in defense applications or added to a resin and molded into preformed pieces, such as vehicle components or wind turbine blades.

ADVANTAGES: Higher strength to weight ratio than steel or aluminum. (tensile and shear strength specifically, but, not the third, compression, see below). Manufacturing process allows for very customized, purpose built parts that meet exact design characteristics, i.e. custom shaped frame tubes with exact dialed in strength in different directions of force, and continuous joints. Good elasticity & shock absorption, which is also 'tunable' based on construction. As for brittleness at low temps, It will not have a problem at normal temps for biking. Higher fatigue strength.

DISADVANTAGES: It's quite expensive. Does not fail as predictably (snaps instead of bending). I think it also has slightly lower compression strength, putting limitations on its use, for example requiring that you don't clamp it too tight in handlebars and posts.

MANUFACTURING PROCESS: Current methods for manufacturing carbon fiber tend to be slow and energy intensive, making it costly for use in mass-produced applications. With a goal of reducing carbon fiber production costs by 50 percent, the Energy Department s new Carbon Fiber Technology Facility at Oak Ridge National Laboratory is working with manufacturers and researchers to develop better and cheaper processes for producing carbon fibers. Lowering the cost of carbon fibers make it a viable solution for vehicles and a wide variety of clean energy applications. As part of conventional carbon fiber production, precursors go through several processes that include stretching, oxidation (to raise the melting temperature) and carbonization in high-temperature furnaces that vaporize about 50 percent of the material, making it nearly 100 percent carbon.

GLASS REINFORCED PLASTIC Glass-reinforced plastic (GRP), is a composite material or fibrereinforced polymer made of a plastic reinforced by fine fibers made of glass. Like carbon fibre reinforced plastic, the composite material is commonly referred to by the name of its reinforcing fibres (fibreglass).

ADVANTAGES It has a good weight to strength ratio. It is water resistant. It is light weight. It is a strong material, so it is feasible. It wont corrode. So you may not even have to finish it by painting it, just have the plastic producer dye it. It doesn't expand or contract anything like steel does. So it wont grow as much in the sun. It is a non-conductive material, so there wont be any galvanising reactions for materials that have to attach to structures.

DISADVANTAGES Although strong, you may need 10-20 times the cross-section, in a compressed state for a designed out, given, piece of steel. Lateral structures you would need to go to formula as far as strength vs size. I would estimate that steel is 100 times as stiff as a horizontal member. If you use glass fibers, you would be creating hazardous waste (somewhere) when it is cut into shapes. The details would be in how it is fabricated. The glue would need to be a resin based material. A process would need to be developed to reliably glue relatively large parts together.

MANUFACTURING PROCESS The easiest method of making a GRP product, e.g. a canoe is to use a mould. The mould may be made from GRP or it may be made from another structurally strong material. The mould is first checked for defects, any scratches are filled. The mould is then polished with a wax polish to a very smooth, high quality finish. Next, a very thin film of a liquid release agent is applied. The wax and the release agent are there to prevent the glass fibre product from sticking to the mould. A layer of resin mixed with a pigment is then applied all over the inside of the mould. This layer is known as a gel coat. When the resin has cured, a layer of reinforcing material such as strand glass fibre is laid inside the mould and a measured amount of polyester resin is stippled and rolled into the reinforcing layer. This layer is also allowed to cure. More layers may be applied until the required thickness is achieved.