Carbon Fibre Cloth Fabric Reinforcement Explained
When choosing the right carbon fibre reinforcement for your project it can be difficult to know what you need and understand the information that is available for each different fabric or material.
The purpose of this guide is to explain what the different specifications mean and how they would relate to a real-world application.
Carbon fibre (fiber) reinforcement is available as a woven fabric, rovings or unidirectional fabric.
Woven fabric is the most common and versatile way to work with carbon fibre. Typically bunches of carbon fibre strands (yarn) are woven bi-directionally (the weft and the warp). The manner in which the weft and the warp are interwoven is the weave pattern.
The most commonly used weave pattern for carbon fibre is '2/2 Twill'. In this pattern the weft goes over two intersecting warps and then under two (hence 2/2) to create a woven fabric with a predominantly diagonal pattern to it. This weave pattern is looser than Plain Weave allowing the fabric to drape more easily which is especially useful when laminating into mould surfaces with compound curves and contours. The looser pattern of the weave means that it must be handled more carefully that plain weave and also that accidental distortion to the weave (relevant where cosmetic appearance is important) is more likely.
Plain weave fabric is the second most widely used of the woven carbon fabrics. In this weave the weft goes over one warp and under the next, creating a grid-like pattern. Plain weave is a slightly tighter weave pattern that 2/2 twill and therefore easier to handle without distorting, however it is not as drape-able as 2/2 twill and therefore it is not the first choice for compound contours.
Braids are continous tubes (or sleeves) of woven carbon fabric. Elongating the braid (stretching it out) will reduce its diameter, allowing braids to be adjusted to be a perfect fit around mandrels or into tubes of varying diameter.
Tapes are simply thin strips (usually supplied on a roll) of woven carbon fabric, most commonly plain weave. Tapes of woven carbon fibre are useful for providing localised reinforcement without the need to cut down large pieces of fabric.
Satin weave, harness weave, fish weave etc are all different weave patterns for carbon fabric although they are used much less widely than 2/2 Twill and Plain Weave. In advanced composites there are almost no situations where these weave patterns are used or are advantageous and so unless you have a very unusual requirement you are unlikely to need or encounter these more obscure weaves.
Rovings is the name given to the bunches of carbon fibres that are usually woven into fabrics. Unwoven rovings are sometimes used as localised reinforcement where they are often wound around a repair.
Unidirectional Carbon Fibre
Unidirectional carbon fibre is a reinforcement where all (or almost all) of the carbon fibres are aligned in the same direction. The only thing holding the fibres together will be occasional strands of either carbon or polyester running across the fibres at 90 degrees. Unidirectional material is used in applications where all of the forces on a part will be in one direction (such as the body of an archery bow). Alternate layers of unidirectional fibres can be positioned with different orientation to allow any combination of bias for the strength of the part to be achieved.