As carbon fiber manufacturers have driven forward their research, carbon fiber plate has come into large scale production along with other carbon fiber construction profiles such as pipe, rod and box sections. In the early days of carbon fiber, the cost of such a product – even if the technology to manufacture it existed, would have been prohibitive. Nowadays it is a stock line for most advanced composites materials distributors.
What is it?
Carbon fiber plates (also known as sheets) are laminated from multiple layers of carbon. Some manufacturers offer a structure in which carbon filaments are unidirectional with each layer being at 90 degrees relative to the layer beneath in the cheapest construction. ‘Quasi Isotropic’ layup includes layers at 45 degrees orientation and offers a more uniform polar strength profile. Others layer woven carbon fabric in the component layers.
With its high fiber-to-resin ratio the construction delivers high strength. A range of surface finishes is available: standard gloss, scratch resistant matte, and texture finishes on one side, with a texture finish on the other side, creating an ideal bonding surface. The textured surface provides an effective key for secondary bonding, though not all suppliers offer the same surface finish on both sides of a sheet.
Some sheet makers offer carbon fiber plate which is backed by a single e-glass layer. Carbon fiber plate construction is not to be confused with laminated sheets which have carbon fiber skins and a core of honeycomb, balsa wood or other material. Carbon fiber plates are solid carbon (apart from the resin, of course).
Typically, plate thicknesses from 0.2mm (‘8 thou’) to 6mm (‘240 thou’) are available as a standard. Sheets of up to 1.5m (5’) by 3m (10’) in size are widely available. The thinnest sheets are known as veneers.
How Carbon Fiber Plate is Made
There are three main methods of manufacture. Simple lay up wetting out the cloth, as might be done with GRP, is finished off with vacuum bagging and room temperature curing of the resin. There is a weight penalty with this relatively inexpensive technique.
The ‘resin infusion’ method involves initial vacuum bagging of the carbon fiber matrix against a finely polished surface. At one end or the perimeter, a supply of resin is injected. Wetting out is very efficient and improved by hydraulic pressure. The lay-up is then oven-cured. The ‘under surface’ finish is somewhat unpredictable and additional resin may be required, adding weight. This technique can also result in pinholes particularly in the thicker sheets. These small imperfections result from a chemical reaction in the epoxy and do not (manufacturers say) affect a sheet’s physical properties.
‘Pre-Preg’ is the most costly manufacturing technique. Resin and hardener are premixed and impregnated into the fabric. The raw composite is laminated to the required thickness which can be controlled very accurately. After bagging, hydraulic or vacuum compression is applied to the matrix and then cured at high temperature. This delivers maximum stiffness and strength with precise weight control whilst the weight of the sheet is minimized.
Types of Resin and Fabric
Standard epoxy resins are used, and lay-ups may include UV resistant polyester gel coats where exposure to high levels of UV may otherwise result in epoxy degradation. ‘Normal tow’ (under 12000 fibers) commonly known as 1k, 3k, 12k weaves are used for the cloths. 2 x 2 3k twill fabric is the most widely used weave, though as previously mentioned, unidirectional filament is also used by some constructors.
With the growth in the use of this material, most advanced countries have several manufacturers:
ACP Composites: http://www.acpsales.com/home.html
Carbon Mods: http://www.carbonmods.co.uk/Default.aspx
Dragon Plate: http://dragonplate.com/default.asp
Carbon Fiber Plate or Metal?
We can’t yet see carbon fiber plate replacing steel but it is replacing metal in many applications where, for example, aluminium would be the metal of choice. Typical uses for carbon fiber plate include Robotics, UAVs, aerospace, motorsport and marine applications, and even musical instruments. Veneers have also been used to strengthen bone fracture repairs in patients with osteoporosis: http://www.ncbi.nlm.nih.gov/pubmed/11938509