Your question doesn't make sense in reference to my response. I didn't assert any claim of knowing something. I was pointing out the lack of a logical link between your evidence and your claim. Even if we are to assume that China has trouble with scaling up the manufacturing of advanced composites at quality levels, a story about some guy trying to ship 2 tons of carbon fiber back to China has utterly no bearing on whether China lacks or has that ability. 2 tons of most any material does nothing for scaling of long term production processes.
If you're trying to argue that China needs/intends to import all their military/aerospace grade materials from abroad then citing a story about how much high quality composites China buys abroad for aerospace purposes would be better evidence. However, the sale of that stuff is regulated and off limits for China. You could make the claim that China will try to steal/illegally import
all the composites they will need for the mass production, but at face value it is an absurd one given the scale of theft/illegal activity that that would have to entail.
That said, questioning whether they will have the capability to manufacture the materials they need at the scale they need them goes back to the assumption that the Chinese and the PLA don't know what they're doing and are just building fancy prototypes for show. It assumes that they're pursuing these ambitious projects with no hard knowledge or plan of how to get to their intended goals. You can assume that if you want (and a lot of these let's doubt China's capabilities articles do seem to assume this), but I think it's important to remember that China and the PLA are not goofy cartoon characters. They are a serious organization and military power, which have had a history of being conservative about their capabilities as well as a history of largely reaching their target goals and delivering on their promises. We are not talking about an Iran or North Korea here. This is a country that has the resources and expertise to do what they say.
Everything aside, we do know China has the ability to manufacture aerospace grade composites because they have partnerships to do just that with both Boeing and Airbus, and if we are to believe what we hear (and see, since you can get an idea of what materials are used on unpainted prototype aircraft), they have been using composites on both the J-10B and J-11B.
