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Advancing Composites - Adding Carbon Fiber to the Designer’s Palette

Mark DeMeuse – Sep 11, 2017

Carbon Fiber CompositesThe versatility, low weight and high strength of carbon fiber makes it the ideal material to use for more commercial, military and industrial applications than perhaps any other substance that is currently available.

Some of the factors that are leading to an increased interest in the carbon fiber market include:


  • Structural and performance advantages
  • Continuous emergence of new and unique applications, and
  • An increased demand from emerging economies

While carbon fiber is more expensive than traditional glass fiber, the stiffness and strength to weight ratios that it provides are significantly higher.

In addition, carbon fiber offers non-corrosiveness, electrical conductivity, and chemical inertness to the products that utilize it in their production. Those benefits are allowing carbon fiber to be used in a wide variety of cutting edge applications that include:

  • Aerospace
  • Transportation
  • Sporting goods
  • Wind energy, and many more
  • Composite applications

Having learnt about the advantages that carbon fiber composite offer, let's see how these benefits are being utilized in the recent technical innovations.


The Recent Technical Innovations with Carbon Fiber


In the past, epoxy has been the most common matrix material that has been used in carbon fiber based composites. The carbon fiber that is used was developed with the epoxy material in mind. However, as the end-use applications have become more challenging and demanding, the need to use other matrix materials has developed. For example, certain thermoplastic polymers are emerging as options for use as the matrix material. Examples of such polymers are polypropylene, polyetherimide and Nylon.

Carbon fiber can be used with each of these matrix polymers. This is one of the great advantages that it provides to new product development. However, as the different matrix materials are being considered, different sizing agents for the carbon fiber need to be developed.

Sizing Agents for Improved Carbon Fiber Performance


Selecting Optimum Sizing Agent The sizing agent acts to improve the adhesion between the carbon fibers and the polymer matrix in which they are embedded. Each particular matrix material has an optimum sizing agent. Much development work is currently ongoing to define the best sizing agent to use with the new polymers with carbon fiber reinforcements.

Techniques that are being utilized to provide different sizing agents for carbon fiber include:

  • Traditional electrolytic treatments
  • Electro-polymerization, and
  • Plasma treatment

The goal of each of these approaches is to find the optimum ratio of the various chemical groups that is needed on the carbon fiber surface for particular applications. It has been found that the optimum sizing agent to be utilized not only depends on the matrix polymer, but can also be related to the particular composite production process that is being utilized. These developments with sizing agents are leading to new uses of carbon fiber in composite structures.

High Strength Carbon Nanotubes for Coatings

High Strength Carbon Nanotubes  A particular innovative development in carbon fibers is related to their production with a coating that is based on carbon nanotubes. The nanotubes can be hundreds of times stronger than steel but only one sixth of the weight. These features make the composites that contain the coated carbon fibers very attractive for use in:

  • Airplanes
  • Cars
  • Trains
  • Spacecraft, and
  • Satellites
In addition, the use of a carbon nanotube coating on the carbon fiber can enhance the electrical conductivity of the carbon fiber material.

In the past, attempts to use a carbon nanotube coating with carbon fiber have resulted in the degradation of the carbon fiber itself. In that situation, the coating is negatively impacting just the effect that it is trying to influence and enhance. Solutions have been sought to improve the degradation effects that have been observed with the previous attempts. Those approaches are meant to not compromise the mechanical integrity of the carbon fibers themselves.

Cause of Fiber DegradationRecently, a team of researchers at MIT has addressed this problem by realizing that the majority of the fiber degradation is due to a lack of tension when the carbon fibers are heated above a certain temperature. They have developed two approaches to deal with that concern.

  1. A unique polymer coating has been developed that adheres to the carbon fiber while also possessing a water-absorbing component that attracts alumina and the metal catalyst.
  2. It was discovered that the need for tension can be eliminated by reducing the temperature of the nanotube growth. The use of the much lower temperature avoids damage to the underlying carbon fiber.

The work at MIT will be very useful in the design of composite materials for use in electrodes and air filters. However, it is still to be proven that the various layers of the fiber and the coatings stay in place during the fabrication of the composite. In addition, the effect of the nanotube attachment on the fiber-matrix adhesion is still to be investigated and explored.


The New Application Areas for Carbon Fibers


#1. Adoption of Carbon Fiber Composites in Electric Cars

One significant avenue for the increased structural use of carbon fiber composites is electric cars. Lightweight materials are well suited for this developing market segment. This is because the driving range on one charge is extremely weight sensitive. In addition, battery placement options are improved by having complex form-fitting structural members. Also, their appearance fits very well with the futuristic picture that electric car makers are trying to achieve in general.

Electric Car Made from Carbon Fiber Composites
Electric Car Based on Use of Carbon Fiber Composites


There are several adoptions of carbon fiber composites in electric cars already. These include rear view mirror casings, spoilers and rear diffusers. In addition, a more widespread use in applications such as seat structures is beginning to emerge. As emissions standards continue to tighten, all cars will require the less weight that is made possible by use of carbon fiber composites.

The new wave of electric cars will promote the merger of the functional and aesthetic roles of carbon fiber composites. Continuous improvement in the composite technology is accelerating the development of these applications. In addition, the data that are being generated on such models will help push carbon fiber composites into more mainstream cars as well.

#2. Carbon Fiber Novel Appearance for Designer Furniture


Electric cars are just one emerging application for carbon fiber composites. For example, designer furniture that is made wholly or partially from carbon fiber composites is blossoming. A wide variety of objects are being offered, some of which hardly need the favorable strength-to-weight ratio that is provided by the carbon fiber. Instead, they take advantage of the formability of the composites. And most important feature - The carbon fiber looks and appeal.

Designer Furniture Based on Use of Carbon Fiber
Designer Furniture Based on Use of Carbon Fiber


There are also innovative furniture uses of the carbon-fiber composites that do take advantage of their strength, even in thin sheets. There are carbon fiber fabric tubes that are forced around party balloons in a chair design. In addition, there are chairs that have several seating positions that are formed from a single, continuous carbon fiber sheet. Overall, the high end furniture market is pushing forward the general acceptance of the use of carbon fiber in the world of architecture and design.

#3. Sporting Goods Applications of Stiff Carbon Fiber Composites


Another area where carbon fiber composites are continuing to make much progress is in sporting goods. They are popular for the use in:

Carbon Fiber Ski
  • Bicycle frames
  • Fishing rods
  • Golf shafts
  • Snow skis
  • Surfboards
  • Tennis rackets, and
  • Other products

They offer compression and lateral stability and also are lightweight. In addition, the carbon fiber composites provide strength and durability to each of the mentioned products.

In these various applications, a great deal of the stiffness is governed by the tube shape and the wall thickness. The use of carbon fiber composites can allow engineers to create the optimal strength and stiffness in key product locations. Composites allow for the creation of more complex shapes and contours.

One recent example of a new development in the sporting goods area is a carbon fiber ski that weighs 200 grams lesser than comparable models. That effect in weight reduction allows for the ski to be very maneuverable and agile on the slopes. In addition, the carbon fiber encloses layers of aluminum and titanium, as well as a wood core. This unique combination of materials enables the optimal stiffness to be achieved while also minimizing torsion, which is related to the twisting of the ski.

It is very important to notice that each of the three application areas that have been discussed for carbon fiber composites utilize a different unique feature that the composite materials provide. Thus, for electric cars, the lightweight nature of the carbon fiber material is exploited. For many of the furniture developments, it is the novel appearance and feel that the carbon fiber possesses that is most attractive. Finally, for use in sporting goods, one of the key features of the carbon fiber composites that are leading to new product developments is - The compression and lateral stability as well as the overall durability.


Conclusion


These general observations indicate that there is more than one feature of the carbon fiber composites that is presently attracting interest in new applications. This suggests that there are further new uses to be expected for the carbon fiber composites.

Applications that take advantage of more than one feature of the carbon fiber are expected to be seen in the near future. Examples of areas where continued new developments are anticipated to occur include the energy and transportation areas. These materials that were initially developed primarily for uses in the aerospace industry are continuing to see new applications.

For many of those applications, the relatively high cost of the carbon fiber compared to glass fiber is not affecting the development. That trend is expected to continue for the foreseeable future for the carbon fiber composite materials in general.



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