engineering

Pitch-based carbon fiber

Pitch-based carbon fiber is a engineering topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Pitch-based carbon fiber rather than just read about it. In short: Carbon fiber is often time produced using two main methods: through the use of Polyacrylonitrile (PAN) and from mesophase pitch. The mesophase pitch forms a thermotropic crystal, which allows the pitch to become organized and form linear chains without the use of tension.

Key takeaways

Pitch-based carbon fiber belongs to engineering; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Pitch-based carbon fiber to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Pitch-based carbon fiber from memory before moving on to harder problems.

Reference excerpt

Carbon fiber is often time produced using two main methods: through the use of Polyacrylonitrile (PAN) and from mesophase pitch. The mesophase pitch forms a thermotropic crystal, which allows the pitch to become organized and form linear chains without the use of tension. Mesophase pitch is made by polymerizing isotropic pitch to a higher molecular weight. The melting point for the mesophase pitch is roughly 300 °C. An advantage in the production of Pitch carbon fibers over PAN carbon fibers is that Pitch carbon fibers do not require constant tension on the fibers at all processing stages. Pitch based carbon fibers have been found to be more sheet-like in their crystal structure, as opposed to PAN based carbon fibers, which are more granular. There are four main steps in the production of carbon fiber from pitch 1) melt spinning 2) oxidization/precarbonization 3) carbonization and 4) graphitization. 1) Melt spinning is the method of forming fibers through the rapid cooling of a melt; due to the fast rates of cooling, the mesophase pitch is able to become highly oriented. Mesophase pitch can be melt spun, but because of its flow characteristics the process can be difficult. The viscosity of mesophase pitch is more sensitive to temperature than other melt-spun materials. Therefore, during the creation of pitch based fibers the temperature and heat transfer rate must be carefully controlled. 2) Oxidization/Precarbonization is used in order to cross-link the fibers to the point where they cannot be melted or fused together. This step is extremely important because it produces fibers that are stable at the high temperatures of carbonization and graphitization; otherwise, the fibers would fail in those steps of the process. It has been reported that the cross-linking is mainly ether formed from C=O or COH. 3) Carbonization is the process removing all non organic elements. In the case of carbon fibers, all elements except for carbon are removed. This is achieved by heating the fibers to high temperatures in an environment without oxygen. This step removes all impurities from the fibers and leaves crystalline carbon structures. These structures are mostly hexagonal in shape and are composed of entirely carbon. 4) Graphitization is the process of treating the fibers at high temperatures in order to improve the alignment and orientation of the crystalline regions along the fiber direction [1,8]. Having the crystalline regions aligned, stacked, and oriented along the fiber direction increases the overall strength of the carbon fiber. The high strength of carbon fiber can be attributed to these four main processes. Having high levels of crystalline regions allows the fibers to withstand high levels of stress. These crystalline regions are formed via the melt spinning process; the crystals are stiff areas that do not deform when an external stress is applied. Orienting and aligning these crystalline regions gives further strength to the fibers, specifically if the orientation is along the fiber axis. Carbonization and graphitization are the two processes responsible for this alignment of the crystalline regions. Pitch based carbon fiber is lower in strength than fiberglass; however, it has a very high elastic modulus. Pitch-based carbon fibers have various end uses due to their high modulus and relatively high strength. These fibers are used within the aerospace industry due to their high modulus, high thermal conductivity, and high electrical conductivity. However, the low production volume of pitch-based carbon fibers, the raw material cost, and the difficulty of production mean that the price is high compared to PAN-based carbon fibers. Pitch-based carbon fibers could be used within the automotive and sports industries, but the higher strength and lower cost of PAN-based carbon fibers makes them more advantageous.

References

Edie, D.D.; Dunham, M.G. (2014). "Melt Spinning Pitch-Based Carbon Fiber". Carbon. 27 (5): 647–655. doi:10.1016/0008-6223(89)90198-X. "How to Turn Pitch into Carbon Fiber for Automotive Applications". AZoM.com. 2020-04-13.

Worked examples

Example 1 — a first encounter with Pitch-based carbon fiber

Start with the simplest possible case. Write down what Pitch-based carbon fiber claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Pitch-based carbon fiber before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Pitch-based carbon fiber ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Pitch-based carbon fiber

In research: Pitch-based carbon fiber appears in engineering research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Pitch-based carbon fiber in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Pitch-based carbon fiber is common in secondary-school and first-year university syllabi. It links to neighbouring topics Composite materials, Synthetic fibers, so understanding it makes those chapters shorter.
In everyday life: Look for Pitch-based carbon fiber outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Pitch-based carbon fiber in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Pitch-based carbon fiber means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Pitch-based carbon fiber out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Pitch-based carbon fiber in simple terms?

Why does Pitch-based carbon fiber matter?

Because it connects several engineering ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Pitch-based carbon fiber?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Pitch-based carbon fiber.