Carbon fibre parts are made by several quite different processes, and a shop is usually set up for one or two of them. Since the process determines the fibre content, the void content and therefore the actual strength of the part, choosing a fabricator is really choosing a process, and a shop that does not ask about your loads is not choosing one for you.
The processes
Wet layup places dry fabric and applies resin by hand: cheap tooling, lowest fibre fraction, most variable. Vacuum infusion draws resin through dry fabric under vacuum, giving better consolidation and repeatability. Prepreg layup uses fabric pre impregnated with resin and cures it under vacuum and heat, usually in an autoclave, giving the highest quality. Compression moulding of chopped or continuous fibre compounds is the volume route.
Why the process decides the strength
Composite strength depends on fibre volume fraction and on void content, and both are consequences of how the resin was introduced and consolidated. A wet laid part and an autoclave cured prepreg part in nominally the same material can differ substantially in performance. Any structural specification therefore has to name the process, not merely the material.
Tooling
Mould tooling has to survive the cure temperature and match the part's thermal expansion, which is why composite tools are often made of composite themselves. Room temperature processes tolerate cheaper tooling in timber, board or filled resin. Autoclave prepreg needs a tool that holds shape at cure temperature and under pressure, and that tool is a significant part of the programme cost.
Questions that reveal a good shop
Which processes they run in house. Whether they can state fibre volume fraction and void content for their process, and how they verify it. How they control prepreg storage life, since prepreg has a shelf life and an out life that both matter. Whether they do non destructive inspection. And whether they will discuss the layup schedule rather than just quoting a shape.
Questions people ask about carbon fiber fabricators
Which composite process is strongest?
Autoclave cured prepreg, because it achieves the highest fibre fraction and the lowest void content. Infusion is next, and wet layup lowest and most variable.
Does the process affect the part's strength?
Substantially. Fibre volume fraction and void content are consequences of the process, so a structural specification must name the process and not only the material.
What tooling do composite parts need?
Tooling that survives the cure temperature and matches the part's thermal expansion, which is why composite tools are often made of composite for heated processes.
What should I ask a composite shop?
Which processes are in house, what fibre volume fraction and void content they achieve and how they verify it, how prepreg storage is controlled, and what inspection they do.