What's the plural form of pre-preg? Here's the word you're looking for.
Answer
The noun pre-preg can be countable or uncountable.
In more general, commonly used, contexts, the plural form will also be pre-preg.
However, in more specific contexts, the plural form can also be pre-pregs e.g. in reference to various types of pre-pregs
or a collection of pre-pregs.