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The physical properties of composites are fiber dominant. It means that when the resin and fiber are combined, their performance remains most like the individual fiber properties. Test data shows that the fibrous reinforcement is the component carrying the majority of the load. For this reason, fabric selection is critical when designing composite structures.
Begin the process by determining the type of reinforcement needed in the project. The average fabricator can choose from three standard reinforcements:fiberglass,carbon fiber, andKevlar®.
Fiberglass tends to be the all-purpose choice, while carbon fiber offers high stiffness and Kevlar®, high abrasion resistance. Our revised "Fundamentals of Fiberglass" white paper includes more fabric selection information for your reference.
Once the fabric family has been determined, select the weight and weave style that suits the demands of the job. The lighter the ounce-weight of the fabric, the easier it will be to drape over highly contoured surfaces. Lightweights also use less resin, so the entire laminate remains lighter. As fabrics become heavier, they become less flexible. Woven roving is the heaviest reinforcement and is typically used in boat building and mould construction.
The way the fabric is woven is considered its pattern or style. Choose from three common weave styles: plain, satin, crowfootand twill. Plain-weave styles are the least expensive and least pliable, but they hold together well when cut.
The frequent over/under crossing of the threads reduces the strength of the plain weaves, although they are still adequate for all but the highest performance applications.
Satin and twill weaves are highly pliable and stronger than plain weaves. In a satin weave, one filling yarn floats over three to seven other warp threads before being stitched under another warp fiber. Threads run straighter much longer in this loosely woven type, maintaining the theoretical strengths of the fiber. Twill weaves offer a compromise between satin and plain styles, as well as an often desirable herringbone cosmetic finish.
To increase the flexibility of thefabric, cut it off the roll at a 45-degree angle to the warpdirection in a bias of 45 degreesand Cut it in a circle.
The fabric drapesbetter over double-curved contours whenthe material is cut in Bias and in a circle way.
Fiberglass is the foundation of the composites industry. It's been used in many composites applications since the 1940s, and its physical properties are pretty well understood. Fibreglass is lightweight, has moderate tensile and compressive strength, is tolerant of both damage and cyclical loading, and is easy to handle.
Fiberglass is the most widely used out of any composite material available.
This is mainly due to its low cost and moderate physical properties.
To maximize the strength properties of the fibreglass, it should be used with anepoxy resin and can be cured using standard lamination techniques (no special tools or methods are required).
It is ideal for aerospace,marine, defence and autoindustries and isused for sporting goods.
Examples of Glassfiber
Style 120 4H Crowfoot Satin E-Glass
Style 1581 8H Satin E Glass
Style 7781 8H Satin E-Glass
Style 7781 tends to replace the 1581 and is a satin weave fabric used for aerospacestructural applications, offering excellent strength and surfacing characteristics.
4 H and 8H. The H means Harnass
Four harness goes over three and under one yarn
8 Harnass goes over seven and under one yarn
E Glasstype means Electric and insulates Low alkali content minimum water absorption
Kevlar® is a registered brand from Du Pont (Original inventor) and is also known as Aramid made by Akzo-Enka called Twaron and Teijin from Japan
Aramid is one of the first high-strength synthetic fibers to gain acceptance in the fibre-reinforced plastic industry
Composites-gradeAramid (Kevlar®) is lightweight, have excellent specific tensile strength, and is touted for highly impacting and abrasion-resistant.
Typical applications include Aircraft Radomes in Aircraft, Leading edges hulls fuselage panels, fan cowl doors and pressure and water vessels.
Nowadays, less Arami in commercial Aeroplanes is used because it absorbs moisture, Oil, and fuel, and they're difficult to repair
Kevlar® (Aramid) is challenging to cut, sand, and machine and is not suited for compressive strength applications. Kevlar®/Aramid should be used with an epoxy or vinyl ester resin.
Laminate Kevlar®/Aramid edgesbetween glass fiber band for ease of cutting/trimming a nice edge.
Ceramic and hardened steel scissors If you are using a ceramic scissor, do not drop them on the floor.
The ceramic blades will break! There also scissorswith Cartledge edges to cut Kevlar®
In case ofrepair,aKevlar/Aramid damage, use a scotsbrite sanding pad (very fine) to finish to repair the surface and make it smoother.
Cover the sanded area with the last cover ply of glassfiber, preventing the Aramid PAN fiberfrom standing up through the paint after sanding.
Style 120 Plain weave
Style 281 Plain Weave
Type 285 4 harness Crowfoot/satin weave
Kevlar 29 High tensile
Kevlar 49 High modules (main aerospace version)
Kevlar 149 High moduelus( low water uptake)
Carbon fibers are PAN based fibers Poly Acrile Nitrile.
Graphite fibers contain up to 95% carbon and yield the highest ultimate tensile strength great compressive strength, and flexural. When processed, these fibers combine to create carbon fiber reinforcement, like fabric, tow, and sleeve. These reinforcements deliver the highest strength and stiffness-to-weight ratio- more than any other standard reinforcement.
Carbon fiber is more expensive than other fibers. And, once you reach the ultimate strength of carbon fiber, it will fail suddenly and snap or splinter.
Explanation: What doe 3k meansasnoted in front of a carbon-weave style number 3k-70PW?
3K means 3000 filaments in one tow
PW means Plain weave
It is different between Carbon and Graphite. Graphite
Use of epoxy:
To maximize the strength properties of a carbonfiber laminate, you have to impregnate itwith anepoxy resinwith excellent capebillities that can be impregnated and use hand lay-up laminating techniques. It used for applications in aviation, aerospaceand other industries.
3k, Plain Weave (PW)
Used For lightweight aircraft parts
This plain weave carbon fiber is a commonly used and selected style, delivers uniform strength in both vertical and horizontal directions.
3k, 2 x 2 Twill Weave (TW2x2)
A Popular carbon fiber fabric weave style, for composite parts with an excellent surface look.
2x2 Twill Weave offers a good drapebillty.
2x2 Twill Weave is used to fabricate composite tooling in the aviation and aerospace industry
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