Chapter 848 Li Yabo's Discovery

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

Sure enough, it was found that around the ablation points on the CFRP board, the surface of the carbon fiber fabric had some pits, but because the background was black, it was impossible to see it more clearly:

"There seems to be carbonization...and drawing and cracking?"

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

Directly refer to the ideas on welding and process 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 visually."

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 grade?"

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 doesn't seem to have any application 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 a generally 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 EDM technology at Liming Factory, which had faced similar problems at the beginning.

Unfortunately, carbon fiber is much more delicate than metal. Problems such as cracking and delamination cannot be solved by polishing.

But the ideas can be used for reference.

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

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 latter ones we just saw, this board is much thinner.

Rather than saying it is a "piece", it is better to say it is a "piece".

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

As thin as a cicada in a literal sense.

However, if those things before could 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 is another matter.

"On boards that are 0.5 millimeters 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. 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 the same as what you saw before.”

"In addition, if you want to drill holes instead of just removing excess base material, then 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 to drill. Rivets... 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 always been 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 miraculous 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 only laser processing is left.

But 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.

Therefore, he still 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 said, found a chair and sat down, and continued half-jokingly:

"Besides, based on your current achievements, you can probably directly apply for Nature..."

What he actually wanted to say was that he could submit it to Nature Materials, a major journal of Nature, but as he was about to say it, he remembered that this journal seemed to have been founded in the early 21st century.

So it stopped abruptly mid-sentence.

"Nature is still too difficult..."

Li Yabo only thought that what Chang Haonan was talking about was 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 ultra-thin 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 could really be used, you would have to register a patent..."

Then he didn’t explain anything more and simply returned to the topic of the paper:

"You can use TORCH Multiphysics or Materials Studio to do a few dynamics 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 it to JACS, or we can wait and send our own JCAS …”

Materials Studio 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 TORCH Multiphysics, its performance in this field is no worse than the latter. .

But this time, Li Yabo did not continue Chang Haonan's words, but suddenly changed the subject:

"Speaking of simulation, teacher, I did use TORCH Multiphysics 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-metal composite materials.

Li Yabo had already sat back in front of the computer:

"As usual, in order to speed up calculations, 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 generally 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.