The military-industrial scientific research system of the academic master.

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

As expected, I found that the surface of the carbon fiber fabric around the ablation points on the CFRP plate was already a bit bumpy, but because the background was black, I couldn't see it more clearly:

"It seems to be carbonized... and there are also wire drawing and cracking phenomena?"

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

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

But if it is accompanied by cracking, it means that there is a problem with the thermal properties of the material itself, and it will not work even if it is put 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 the failure of the colloid, but this requires a probe to see it specifically. I have an appointment for next week."

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

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

"What about lowering the rating?"

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

Just like some defective CPUs will have a few cores blocked and sold as lower-end models, if a T700 that has failed in processing can still be used as a T500, 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, we cannot take this risk."

"That doesn't seem to have any practical value..."

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

At this time in 2000, China was still working hard to move from the poverty line to overall well-off, and products such as carbon fiber bicycles or fishing rods obviously could not find a market.

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

It’s a pity that carbon fiber is much more delicate than metal, and problems like cracking and delamination obviously cannot be fixed by polishing.

However, the ideas can be used as reference.

"Have you ever considered using a thinner laser beam and then drilling the holes gradually in a circular or spiral trajectory?"

Chang Haonan suggested:

"This way the laser is not continuously acting on the same point, and the ablation effect should be weakened."

"I tried."

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

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

It is more accurate to say that it is a "piece" rather than a "piece".

Chang Haonan estimated with his naked eyes that the thickness might not even be one millimeter...

Literally as thin as a cicada's wing.

However, if the previous ones could only be called progress, then what the board in his hand represented could be considered a real achievement.

Of course, the specific application value is another matter.

“On boards that are 0.5 millimeters or thinner, this can actually work.”

Li Yabo said this as he carefully took the thin plate from Chang Haonan's hand and shone it under the light on the ceiling of the laboratory.

Even slightly translucent.

Then he continued:

"However, for such a thin plate, even machining is easy, and this thin plate itself has almost no practical value. It is too thin even to be used as aircraft skin."

"But if the plate is thicker, such as 5 mm or even 1 cm, then both circular cutting and spiral cutting cannot be completed in one cycle. If repeated many times, the thermal effect will accumulate, and the final result will be similar to what you have seen before."

"In addition, if you want to drill holes instead of just remove 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 not convenient for rivets... In short, the subsequent processing is also very troublesome, and in the end it is better to use special tools for mechanical removal."

That’s right, the reason why it’s difficult to increase the application of carbon fiber is mainly because the way of processing carbon fiber is almost the same as processing metal.

However, the characteristics of carbon fiber determine that using ordinary cutting tools can easily lead to problems such as material tearing, fiber pulling out, and excessive residual stress.

Therefore, the processing cost and working hours of carbon fiber components, especially carbon fiber structural parts, have remained high. Even long-range wide-body passenger aircraft with high prices and extremely high profit margins cannot withstand large-scale use.

Even more than 20 years later, mechanical processing is still the most mainstream method for composite material 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 not feasible for China in 2000.

That's why Chang Haonan suggested that Li Yabo focus on some tricks and tricks.

For example, laser or water jet.

The latter was strategically abandoned after checking some information.

So the only option left is laser processing.

However, judging from Li Yabo's experimental results, the current effect seems to be worse than mechanical processing.

The latter at least has no thermal effect...

However, Chang Haonan was not too anxious.

According to the original timeline, the aerospace field truly achieved "large-scale" application of carbon fiber composites, especially those involving structural parts, after 2010.

Therefore, he still comforted the somewhat disappointed Li Yabo:

"It doesn't matter. Your project has only been underway for less than a month. There's still plenty of time..."

Chang Haonan found a chair and sat down, then continued half-jokingly:

"Besides, based on your current achievements, you can probably submit them directly to Nature..."

What he actually wanted to say was that he could submit to Nature Materials, a major sub-journal of Nature, but when the words were on his lips he remembered that this journal seemed to have been founded only in the early 21st century.

So the story stopped halfway.

“Nature is still too difficult…”

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

"The idea of ​​using laser to process carbon fiber was proposed about four or five years ago. I just pushed it a little bit forward, and there is no application value in processing ultra-thin plates."

Chang Haonan waved his hand:

"You are allowed to publish it casually because it has no application value. If it can really be used, you have to register a patent..."

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

"You can use TORCH Multiphysics or Materials Studio to do a few more dynamic simulations. It's not a big problem if the results are less accurate, as long as they can be explained from a qualitative perspective. Then you can publish it in JACS, or wait a little longer and publish 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 TORCH Multiphysics content, 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, sir, I did use TORCH Multiphysics to simulate the effects of overheating and ablation on CFRP materials."

"what's the result?"

Chang Haonan did not have high expectations for the simulation accuracy of non-metallic composites.

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

"As a rule, in order to speed up the calculation, we only simulate the ablation effect for 10ms. It is indeed the same as you said before. The accuracy on carbon fiber is very poor."

"But a few days ago, I entered the wrong simulation duration before going to bed. I entered 1000ms, which is 1 second. The next day, I found that the computer had calculated it all night. As a result, the simulation accuracy was much higher than before."

"Later, I divided the groups into several different tests and found that the longer the simulation time, the higher the accuracy compared with the experimental results. I guess it may be because there is some highly random mechanism, which is more obvious when the time is short, but tends to be average after a long time..."

Chang Haonan was already preparing to leave.

But when he heard Li Yabo say this, he stopped again.