Skip to Content

Answers provided by John Linck on Challenges and Opportunities

Daniel_Melo's picture

Q.: Can we add "the cutting challenge of Carbon Fiber Laminate"? For example, it is hard to use laser cutting.
A.: It is my understanding that water jet cutting and the use of diamond tools are the most common means of machining polymer matrix composites. Due to high differential temperature capability between the fiber and the matrix, the use of laser cutting is more challenging. Very high power is required to cut the carbon fiber due to its lack of a melting point.

Q.: Can you mention which type of carbon precursor is getting more important today pitch or pan based carbon fiber?
A.: PAN by far. Move than 90% of the carbon fiber used today is PAN based. Pitch fibers are used predominantly for high thermal conductivity applications.

Q.: What would you say the approximate cost breakdown is between raw materials, manufacturing, and design/testing?
A.: I have a chart from SGL that shows the following breakdown but does not include testing.
Raw material: 25%
Fabric cutting and layup: 50%
Molding: 20%
Machining: 5%

I would guess that testing is probably somewhere in the 5% range.

Q.: Any feedback on EMI shielding?
A.: EMI shielding is driven by reflection and absorption. Metals are generally better for EMI shield due in part to their high conductivity. Carbon fibers are good conductors but polymer matrices aren’t. Efforts to improve EMI shielding involve adding metallic or other fillers to the matrix to improve conductivity. Metals are heavy so not the best for maintaining lightweight. There is a lot of effort going on today to incorporate high thermal conductivity fillers including carbon black, graphene nanoplatelets and carbon nanotubes to increase the matrix conductivity and remain lightweight. There are several good papers on the subject prepared by Dr. D.D.L. Chung, State University of New York at Buffalo.

Q.: How would you educate / motivate new customers?
A.: Focus on manufacturing techniques and benefits of design optimization.

Q.: What are the main competitors for composites?
A.: In my opinion, magnesium and lithium aluminum alloys.

Q.: Other than weight (and the "cool" factor), are there areas where we have identified composites have a clear advantage over metals or other materials?
A.: Stiffness and strength to weight ratio.

Q.: Any information on the embodied energy of carbon fiber (kJ/kg)?
A.: I’m not sure I understand the question. Carbon fibers can withstand very high temperatures; however, polymer matrices generally cannot. Carbon/carbon composites solve the energy absorption problem as the matrix is carbon as well. However, carbon-carbon composites are generally very expense compared to polymer matrix composites so applications are limited to very high temperatures.

Q.: We live in an age of optimization. What is the industry doing to collaborate with traditional materials?
A.: Polymer matrix composites are not the best for all applications. In my opinion, industry should focus on applications that make the most sense for the material. For example, I personally feel that the benefits of using carbon fiber-based polymer matrix composites for automotive body panels is limited. Far more weight benefit can be realized if carbon can be used in primary load bearing structures. This is part of why I believe BMW is on the right track with the i3 and i8. They are making the passenger cell out of carbon fiber which is where they are getting the most advantage.