Fiberglass part 3.pdf

Fiberglass - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Fiber_glass

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Diagram of the pultrusion process.

Construction methods

Fiberglass hand lay-up operation

A release agent, usually in either wax or liquid form, is applied to the chosen mold. This will allow the finished product to be removedcleanly from the mold. Resin—typically a 2-part polyester, vinyl or epoxy—is mixed with its hardener and applied to the surface. Sheetsof fibreglass matting are laid into the mold, then more resin mixture is added using a brush or roller. The material must conform to themold, and air must not be trapped between the fiberglass and the mold. Additional resin is applied and possibly additional sheets offiberglass. Hand pressure, vacuum or rollers are used to make sure the resin saturates and fully wets all layers, and any air pockets areremoved. The work must be done quickly enough to complete the job before the resin starts to cure, unless high temperature resins areused which will not cure until the part is warmed in an oven.[6] In some cases, the work is covered with plastic sheets and vacuum isdrawn on the work to remove air bubbles and press the fiberglass to the shape of the mold.[7]

Fiberglass spray lay-up operation

The fiberglass spray lay-up process is similar to the hand lay-up process but the difference comes from the application of the fiber andresin material to the mold. Spray-up is an open-molding composites fabrication process where resin and reinforcements are sprayedonto a mold. The resin and glass may be applied separately or simultaneously "chopped" in a combined stream from a chopper gun.Workers roll out the spray-up to compact the laminate. Wood, foam or other core material may then be added, and a secondary spray-uplayer imbeds the core between the laminates. The part is then cured, cooled and removed from the reusable mold.

Pultrusion operation

Pultrusion is a manufacturing method used to make strong, lightweight compositematerials, in this case fiberglass. Fibers (the glass material) are pulled from spoolsthrough a device that coats them with a resin. They are then typically heat-treated and cutto length. Pultrusions can be made in a variety of shapes or cross-sections such as a W orS cross-section. The word pultrusion describes the method of moving the fibers throughthe machinery. It is pulled through using either a hand-over-hand method or a continuous-roller method. This is opposed to an extrusion, which would push the material throughdies.

Chopped strand mat

Chopped strand mat or CSM is a form of reinforcement used in fiberglass. It consists of glass fibers laid randomly across each otherand held together by a binder.

It is typically processed using the hand lay-up technique, where sheets of material are placed in a mold and brushed with resin. Becausethe binder dissolves in resin, the material easily conforms to different shapes when wetted out. After the resin cures, the hardenedproduct can be taken from the mold and finished.

Using chopped strand mat gives a fiberglass with isotropic in-plane material properties.

WarpingOne notable feature of fiberglass is that the resins used are subject to contraction during the curing process. For polyester thiscontraction is often of the order of 5-6%, and for epoxy it can be much lower, about 2%.

When formed as part of fiberglass, because the fibers don't contract, the differential can create changes in the shape of the part duringcure. Distortions will usually appear hours, days or weeks after the resin has set.

While this can be minimised by symmetric use of the fibers in the design, nevertheless internal stresses are created, and if thesebecome too great, then cracks will form.

Health problemsThe National Toxicology Program ("NTP"), in June 2011, removed from its Report on Carcinogens allbiosoluble glass wool used in home and building insulation and for non-insulation products.[8]

However, NTP classifies as Fibrous Glass Dust "Reasonably anticipated to be a human carcinogen[9]





Air flow test for the extraction andfiltration of styrene vapors in aproduction hall for GRP yachts

Kayaks made of fiberglass

The National Toxicology Program ("NTP"), in June 2011, removed from its Report on Carcinogens allbiosoluble glass wool used in home and building insulation and for non-insulation products.[8]

However, NTP classifies as Fibrous Glass Dust "Reasonably anticipated to be a human carcinogen(Certain Glass Wool Fibers (Inhalable))".[9] Similarly, California's Office of Environmental HealthHazard Assessment ("OEHHA"), in November 2011, published a modification to its Proposition 65listing to include only "Glass wool fibers (inhalable and biopersistent)."[10] The U.S. NTP andCalifornia's OEHHA action means that a cancer warning label for biosoluble fiber glass home andbuilding insulation is no longer required under Federal or California law. All fiber glass woolscommonly used for thermal and acoustical insulation were reclassified by the International Agency forResearch on Cancer ("IARC") in October 2001 as Not Classifiable as to carcinogenicity to humans(Group 3).[11]

The European Union and Germany classify synthetic vitreous fibers as possibly or probablycarcinogenic, but fibers can be exempt from this classification if they pass specific tests. Evidence forthese classifications is primarily from studies on experimental animals and mechanisms ofcarcinogenesis. The glass wool epidemiology studies have been reviewed by a panel of internationalexperts convened by the International Agency for Research on Cancer ("IARC"). These experts concluded: "Epidemiologic studiespublished during the 15 years since the previous IARC monographs review of these fibres in 1988 provide no evidence of increased risksof lung cancer or mesothelioma (cancer of the lining of the body cavities) from occupational exposures during the manufacture of thesematerials, and inadequate evidence overall of any cancer risk."[11] Similar reviews of the epidemiology studies have been conducted bythe Agency for Toxic Substances and Disease Registry ("ATSDR"),[12] the National Toxicology Program,[13] the National Academy ofSciences[14] and Harvard's Medical and Public Health Schools[15] which reached the same conclusion as IARC that there is no evidenceof increased risk from occupational exposure to glass wool fibers.

Fiberglass will irritate the eyes, skin, and the respiratory system. Potential symptoms include irritation of eyes, skin, nose, throat,dyspnea (breathing difficulty); sore throat, hoarseness and cough.[16] Scientific evidence demonstrates that fiber glass is safe tomanufacture, install and use when recommended work practices are followed to reduce temporary mechanical irritation.[17]

Fiberglass is resistant to mold but growth can occur if fiberglass becomes wet and contaminated with organic material. Fiberglassinsulation that has become wet should be inspected for evidence of residual moisture and contamination. Contaminated fiberglassinsulation should be promptly removed.[18]

While the resins are cured, styrene vapors are released. These are irritating to mucous membranes and respiratory tract. Therefore, theHazardous Substances Ordinance in Germany dictate a maximum occupational exposure limit of 86 mg/m³. In certain concentrationsmay even occur a potentially explosive mixture. Further manufacture of GRP components (grinding, cutting, sawing) goes along with theemission of fine dusts and chips containing glass filaments as well as of tacky dust in substantial quantities. These affect people's healthand functionality of machines and equipment. To ensure safety regulations are adhered to and efficiency can be sustained, theinstallation of effective extraction and filtration equipment is needed.[19]

Examples of fiberglass useSurfboards, tent polesGliders, kit cars, sports cars, microcars, karts, bodyshells, boats, kayaks, flat roofs, lorries, K21Infantry Fighting VehicleMinesweeper hullsPods, domes and architectural features where a light weight is necessaryHigh end bicycles[citation needed]

Bodyparts for and entire automobiles, such as the Anadol, Reliant, Quantum Quantum Coupé,Chevrolet Corvette and Studebaker Avanti, and DeLorean DMC-12 under bodyAntenna covers and structures, such as radomes, UHF broadcasting antennas, and pipes usedin hex beam antennas for amateur radio communicationsFRP tanks and vessels: FRP is used extensively to manufacture chemical equipment and tanksand vessels. BS4994 is a British standard related to this applicationMost commercial velomobilesMost printed circuit boards used in electronics consist of alternating layers of copper and fibreglass FR-4Large commercial wind turbine bladesRF coils used in MRI scannersSub sea installation protection coversRe-enforcement of asphalt pavement, as a fabric or mesh interlayer between lifts[20]

Protective helmets used in various sportsOrthopedic casts[21]

Fiberglass Grating is used for walkways on ships, oil rigs and in factoriesFiber reinforced composite columns





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Fiberglass part 3.pdf