May 20th 2021
Carbon fiber, aramids & hybrids are pretty incredible fabrics which can be used in a myriad of ways and applications. What makes them so useful & versatile? In this post we’ll look at the various properties & resistances of the three main types of Carbon Fibers.
Thermal Conductivity is simply the material’s ability to transfer or carry heat. It is measured by the transfer rate of which heat will flow through the given source (material). Higher thermal conductivity means that the heat transfer will occur at higher rates. Thermal conductivity in composites is anisotropic, meaning that the heat will be transferred through faster in the fiber direction. Overall thermal conductivity relies heavily on volume fraction of resin to fiber and the compactness of the fibers as the fibers carry out the heat transfer. It is important to note that the overall design of the composite structure plays a more important part in the thermal conductivity in a composite than the fiber itself.
Flammability Properties of these fibers conclude that they are all resistant to high temperatures. Carbon Fibers and Kevlar as fabrics are used commonly together for firefighting and protective clothing. Matted Glass fibers are commonly used in buildings to improve fire resistance. However, when used in a composite matrix, temperatures of the composite are limited to that of the resin’s heat capability.
Electrical Properties of material’s are defined by a fiber’s ability to conduct electric current, it’s resistance to current and any shielding effects in the electromagnetic spectrum. These properties are mainly only of concern regarding carbon fibers. Because Carbon Fiber is conductive, it is subject to causing Galvanic Corrosion on metallic parts. In response, industrial applicators have insulated metal parts bonded to carbon fiber or added layers of fiberglass in areas of contact in prevent this occurrence. Carbon Fibers have challenged aerospace designers and industry alike as its electrical properties must be designed around and are still being researched.
Fiberglass and Kevlar composites are virtually transparent to radio waves and do not conduct electricity. It is for this reason that Kevlar is commonly used in electrical transmission towers. (With the Kevlar being coated to prevent water absorption)
Chemical Resistivity is a material’s ability to withstand exposures to differing chemical agents along the pH scale and how a fiber reacts within a given time frame. These are widely tested in exposing fibers to such conditions as Water (Fresh & Sea), Organic Solvents, Strong Acid, Strong Alkalis, Weak Acid, and Weak Alkalis.
Carbon fibers are very strong in terms of chemical resistance and do not have great sensitives to any of the above with the expectation to strong oxidizing agents. Fiberglass is comparable to that of Carbon Fiber with a weak reaction to Strong Alkalis.
Kevlar is not suspectable to organic solvents or oils but has shown to degrade in the presence of strong acids, bases, and some oxidizing compounds. Chemicals such as bleach should not be used with Kevlar fibers. Kevlar is also degraded by UV radiation and sunlight.
Overall chemical resistivity of composites relies heavily on the resins used in the composite structure.