Understanding CFRP Composites

The Amazing Capabilities of Carbon Fiber Reinforced Polymers

Carbon Fiber Cloth
Carbon fiber cloth used in composites. Creative Commons: Erik Charlton via Flickr

CFRP Composites are lightweight, strong materials used in the manufacturing of numerous products used in our daily life. Carbon Fiber Reinforced Polymer Composites, or CFRP Composites for short, is a term used to describe a fiber reinforced composite material that uses carbon fiber as the primary structural component. It should be noted that the "P" in CFRP can also stand for "plastic" instead of "polymer."

In general, CFRP composites use thermosetting resins such as epoxy, polyester, or vinyl ester. Although thermoplastic resins are used in CFRP Composites, "Carbon Fiber Reinforced Thermoplastic Composites" often go by their own acronym, CFRTP composites.

When working with composites or within the composites industry, it is important to understand the terms and acronyms. More importantly, it is necessary to understand the properties of FRP composites and capabilities of the various reinforcements such as carbon fiber.

Properties of CFRP Composites

Composite materials, reinforced with carbon fiber, are different than other FRP composites using traditional materials such as fiberglass or aramid fiber. The properties of CFRP composites which are advantageous include:

Light Weight - A traditional fiberglass reinforced composite using continuous glass fiber with a fiber of 70% glass (weight of glass / total weight), will commonly have a density of .065 pounds per cubic inch.

Meanwhile, a CFRP composite, with the same 70% fiber weight, might typically have a density of .055 pounds per cubic inch.

Stronger - Not only are carbon fiber composites lighter weight, but CFRP composites are much stronger and stiffer per unit of weight. This is true when comparing carbon fiber composites to glass fiber, but even more so when compared to metals.

For example, a decent rule of thumb when comparing steel to CFRP composites is that a carbon fiber structure of equal strength ​will often weigh 1/5th that of steel. You can imagine why all the automotive companies are investigating using carbon fiber instead of steel.

When comparing CFRP composites to aluminum, one of the lightest metals used, a standard assumption is that an aluminum structure of equal strength would likely weigh 1.5 times that of the carbon fiber structure.

Of course, there are many variables that could change this comparison. The grade and quality of materials can be different, and with composites, the manufacturing process, fiber architecture, and the quality need to be taken into account.

Disadvantages of CFRP Composites

Cost - Although amazing materials, there is a reason why carbon fiber is not used in every single application. At the moment, CFRP composites are cost prohibitive in many instances. Depending on the current market conditions (supply and demand), the type of carbon fiber (aerospace vs commercial grade), and the fiber tow size, the price of carbon fiber can vary dramatically.

Raw carbon fiber on a price per pound can be anywhere between 5-times to 25-times more expensive than fiberglass.

This disparity is even greater when comparing steel to CFRP composites.

Conductivity - This can be both an advantage to carbon fiber composites, or a disadvantage depending on the application. Carbon fiber is extremely conductive, while glass fiber is insulative. Many applications use glass fiber, and cannot use carbon fiber or metal, strictly because of the conductivity.

For example, in the utility industry, many products are required to use glass fibers. It is also one of the reasons why ladders use glass fiber as the ladder rails. If a fiberglass ladder were to come in contact with a power line, the chances of electrocution are much lower. This would not be the case with a CFRP ladder.

Although the cost of CFRP composites still remains high, new technological advancements in manufacturing are continuing to allow for more cost effective products.

Hopefully, in our lifetime we will be able to see cost-effective carbon fiber used in a wide range of consumer, industrial, and automotive applications.