Composite Fabrication Methods

There are numerous methods for fabricating composite components. Some methods have been borrowed (injection molding from the plastic industry, for example), but many were developed to meet specific design or manufacturing challenges faced with fiber-reinforced polymers.

Carbon Fiber and other Composite fabrication processes typically involve some form of molding, to shape the resin and reinforcement. A mold tool is required to give the unformed resin/fiber combination its shape prior to and during cure.

 

Choice of fabrics

Choosing a fabric type is mostly dependant on two factors – weave type and thickness.  Determining the weave type is based upon your aesthetic and conformability requirements.  The most common fabric chosen for aesthetic applications is typically a 3K 2×2 twill for carbon fabric applications.  This fabric provides the most elegant look of all weave types.  One of the most flexible fabrics is generally a twill weave (note that a 4×4 twill will be more flexible than a 2×2).  The least conforming fabric is a plain weave.

 

What thickness you need in a particular fabric is dependent on your application.  For cosmetic purposes using carbon fiber fabric, a 3K carbon is often an ideal choice.  For structural applications, the most cost effective solution is to use the thickest possible fabric.  Thicker fabrics are cheaper per sqm than multiple layers of thinner fabrics, although thinner fabrics will generally conform better to complex curves than thicker fabrics.

 

 

The Overlay Method

The overlay method is the simplest of all the laminating methods.  Generally it involves finding an existing piece and sanding it lightly, then carbon fiber or other composite fabric is laid over the top of this existing piece, and resin is applied.  Finishing such a piece using the overlay method generally involves one of two techniques.  The first is sanding and/or buffing the finished overlay composite piece to a shine.  The second option is to sand the piece smooth, then apply a final coat of resin or add a clear coat, typically of urethane for epoxy, or a polyester clear coat for a polyester based resin.The overlay method is commonly used when one custom piece needs to be made, or a small number of custom pieces need to be made.  The main disadvantage of using the overlay technique is that results can be inconsistent and one often needs to be at least somewhat “crafty” in order to be able to create professional looking pieces.

You can choose one of our laminating carbon fiber kits here  

 

Vacuum Bagging

Vacuum bagging is by far the most complex and expensive of all the methods, but usually results in the best final product.  The first step in vacuum bagging is to create a perfectly designed reverse mold of the final piece which you intend to make.  This mold can be made out of virtually any material, anything from silicon rubber molds to composite.  The second step involves laying your carbon fiber or other composite fabric(s) into your newly created mold, then applying either a release fabric for fairly flat products or a peel-ply for complex and curvy applications.  A release fabric is typically a plain weave nylon treated fabric that allow resin to pass through it, but the release fabric itself will not stick to the composite product.  A peel-ply is a stretchable rubber like membrane with small holes space throughout the membrane, allowing resin to be sucked through those holes.  Behind the peel-ply or release fabric you place a breather fabric.  The purpose of the breather fabric is to absorb the excess epoxy being pulled through the release fabric or peel-ply.  Behind the breather fabric is the vacuum bag itself.  This acts as a permanent barrier and helps create an airtight chamber so that the resin can be sucked away from the product.  Sealing the bag to the mold requires a special sticky tape.  This tape provide an airtight seal between the mold and the vacuum bag itself.  This tape is commonly referred to as sealant tape.

 

If producing large numbers of identical units, such as if you intend to go into production making one specific piece or product, vacuum bagging is an ideal method.  The disadvantages of using a vacuum bagging method are that it often requires a great deal of effort to create a perfect mold; it also often requires adjusting of the vacuum bag line(s) and possibly adjusting the individual suction of each line.  Because of this, it is common to go through at least three to five pieces until you perfect your product and are ready to go into production.  Therefore this method is generally not recommended if your intention is to create only a few specific pieces.

 

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