There might be something more to add on. If you want to make a part that will last a lifetime it would probably be too heavy and actually hurt other parts of the body because of its rigidity. Considering that the part will be interfacing with human body it should be allowed to flex to a certain extent, and flexing will always destroy a part gradually.

We are just speculating since we don't know how it looks like.
Instead of making a bulletproof, ultra tough, ultra high strenght thing I would rather investigate the possibility of making a very very easy to use mould which you could use to make the braces at different intervals (2 years or 5 or 10, don't know). Just layup let it cure and you can have another one in a few hours.

Parts that need to interface with human body should not be rigid, even our bones flex, so the brace should flex too, which will destroy it in time. Better to have an easy to use mould so you can be independant of insurance companies.

I don't think the doc can make a perfect brace the first time - it will either be too rigid or too soft, if you have the mould you can make trials at home with different layups untill satisfied.

Regards,