The Military-industrial Scientific Research System of the Academic Master Chapter 848

Chapter 848 Li Yabo's discovery

After listening to Li Yabo's explanation, Chang Haonan also walked forward and took a look in front of the microscope's eyepiece.

As expected, we found that around the ablation points on the CFRP board, the surface of the carbon fiber fabric had some bumps and pits, but because the background was black, we couldn't see it more clearly:

“It seems like there's carbonization… and there's also stringing and cracking?”

If the problem is only carbonization, it is relatively easy to deal with.

Just refer to the idea of welding directly and process it in an inert gas environment.

But if it is still accompanied by cracking, it means that it is a problem with the thermal properties of the material itself, even if it is thrown into vacuum processing.

We can only consider solving the problem fundamentally.

“This is what you can see with your eyes.”

Li Yabo nodded:

"In addition, I have also measured the mechanical properties and found that the static strength, especially the anisotropic tensile strength, will drop a lot, so I suspect that there is a delamination problem inside the material due to colloid failure, but this requires a probe. The needle can be seen in detail, and I have an appointment for next week.”

If the laboratory does not have equipment, it can only be handed over to a unified testing agency, and the efficiency will definitely be affected to some extent.

However, this problem has no solution for the time being, so Chang Haonan decided to focus on other aspects first.

“What about lowering the label?”

He picked up a CFRP board from the side and asked Li Yabo.

Just like some defective CPUs will have a few cores removed and sold as lower-end models, if the T700 that failed to be processed can still be used as a T500, then a higher loss rate may not be unacceptable.

However, the latter immediately gave a negative answer:

“No, the degree of performance degradation is very unstable. Sometimes very different performance parameters can be measured at different locations on the same board. At least in the aerospace field, this risk cannot be taken.”

“That really seems to have no practical value…”

Chang Haonan had no choice but to give up this second-best idea.

In 2000, China was still striving to move from a subsistence level to an overall well-off society. Products such as carbon fiber bicycles or fishing rods obviously could not find a market.

At this time, he suddenly thought of the electric discharge machining technology at Liming Factory, which had faced similar problems at the beginning.

It's a pity that carbon fiber is much more delicate than metal. Problems such as cracking and delamination cannot be solved by polishing.

However, the ideas can be used for reference.

“Have you ever considered using a thinner laser beam and then gradually punching out the hole in a circular or spiral path?”

Chang Haonan suggested:

“In this way, the laser does not continuously act on the same point, and the ablation effect should be weakened.”

"I tried."

Li Yabo took another CFRP board from the sample rack next to it and handed it to Chang Haonan.

Compared to the ones we just saw, the thickness of this board is much thinner.

It is better to say that it is a “piece” than a “piece”.

Chang Haonan estimated it with the naked eye and found that the thickness may not even be one millimeter...

Literally as thin as a cicada's wings.

However, if what was done before can only be called progress, then what the board in his hand represents can be regarded as a serious achievement.

Of course, the specific application value will be discussed separately.

“On boards that are 0.5 mm or thinner, this really works.”

Li Yabo said as he carefully took the thin plate from Chang Haonan's hand and shined it on the light on the top of the laboratory.

Even slightly translucent.

Then he continued:

“However, for such a thin plate, even mechanical processing is very easy, and the thin plate itself has almost no practical value, and it is too thin even to be used as an aircraft skin.”

"But if the board is thicker, such as 5 millimeters or even 1 centimeter, then whether it is circumferential cutting or spiral cutting, it will not be possible to complete the processing in one cycle. And if it is repeated many times, the thermal effect will accumulate, and the final result will be The result is still similar to what you saw before. "In addition, if you want to drill holes instead of just removing excess base material, this cutting method can only handle holes of up to 2mm, whether it is bolts or rivets... No. , composite materials have no ductility and are inconvenient for riveting... In short, the subsequent processing is also very troublesome. In the end, it is better to use special tools for mechanical removal. "

Yes, the reason why the application of carbon fiber is difficult to increase is mainly because the method of processing carbon fiber is almost the same as processing metal.

However, the characteristics of carbon fiber determine that using ordinary tools can easily cause material tearing, fiber pulling out, and excessive residual stress.

Therefore, the processing costs and labor hours of carbon fiber parts, especially carbon fiber structural parts, have remained high. Even long-range wide-body passenger aircraft with high prices and extremely high profit margins cannot help but use them in large quantities.

Until more than 20 years later, the most mainstream composite processing method is still mechanical processing. It is just that technicians have greatly reduced processing losses through years of massive practical experience and vigorous mechanical calculations.

However, these two methods were obviously unqualified for China in 2000.

That's why Chang Haonan suggested that Li Yabo focus on some strange skills.

Such as laser or water jet.

The latter was strategically abandoned after checking some information.

So the only way left is laser processing.

Just as far as Li Yabo's experimental results are concerned, the current effect seems to be worse than mechanical processing.

The latter has no thermal effect at least...

However, Chang Haonan was not too anxious.

According to the original timeline, the real "large-scale" application of carbon fiber composites in the aerospace field, especially when it comes to structural parts, will only happen after 2010.

So, he comforted the somewhat disappointed Li Yabo with a few words:

“It doesn't matter, your project has only started less than a month ago, and there is still plenty of time…”

Chang Haonan found a chair to sit down as he spoke, and continued half-jokingly:

“Besides, based on your current achievements, you can probably directly invest in Nature...”

What he actually wanted to say was that he could submit his paper to Nature Materials, a major journal of Nature. But as he was about to speak, he remembered that this journal was only founded in the early 21st century.

So it stopped abruptly in the middle of the sentence.

“Nature is still too difficult...”

Li Yabo thought Chang Haonan was talking about nature itself, and immediately shook his head:

“Using laser to process carbon fiber is an idea that someone proposed about four or five years ago. I just pushed it a little further, and processing ultrthin plates has no application value.”

Chang Haonan waved his hand:

“It's just because it has no application value that I let you distribute it casually. If it was really useful, you would have to register a patent...”

Then without further explanation, he simply returned to the topic of the paper:

“You can use TORC Multiphysics or Materials Studio to do a few dynamic simulations. The accuracy of the results is not a big problem, as long as it can be explained from a qualitative perspective. Then we can send a JACS, or wait and send our own JCAS..."

MaterialsStudio is a numerical calculation software developed by Accelrys in early 2000. Because it specializes in molecular dynamics calculations and also draws on a lot of content from TORC Multiphysics, its performance in this field is no worse than the latter.

But this time, Li Yabo did not continue what Chang Haonan said, but suddenly changed the subject:

“Speaking of simulation, teacher, I did use TORCMultiphysics to simulate the effect of superheated ablation on CFRP materials.”

"what's the result?"

Chang Haonan does not have high expectations for the simulation accuracy of non-metallic composite materials.

Li Yabo has now sat back in front of the computer:

“As usual, in order to speed up the calculation, we only simulate the ablation effect of 10ms. Indeed, as you said before, the accuracy on carbon fiber is very poor.”

"But a few days ago, I once entered the wrong simulation duration before going to bed. I entered it as 1000ms, which is 1 second, and then the next day I found that the computer had already calculated it all night. As a result, the accuracy of the simulation was better than It was much higher in the past.”

"Later, I conducted several different tests in groups, and found that in general, the longer the simulation time, the higher the accuracy compared with the experimental results. I guess it may be because there is some kind of highly random mechanism. It's more obvious in the short term, but it will tend to average over time…”

Chang Haonan was already ready to leave.

But when Li Yabo said this, he suddenly stopped again.

(End of this chapter)

Chapter end

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