Pultrusion or Vacuum injection moulding?

[carbongr]

Which method can give better results in respect of rigidity, when we manufacture flat sheets/bars using UD carbon fibre?
What is the best resin/fabric weight ratio to achieve this?
Thanks in advance

 

[GBor]

I suppose it depends on the quality of your manufacturing, but I would suspect pultrusion for uni-directional. Vacuum bag has a tendency to slightly shift the fibers as it draws down.

 

[RPstress]

Some general advice is possible, but without knowing more about the form of structure to be made it's hard to be genuinely helpful.

Pultrusion with unidirectional fibres can give 70% fibre volume fraction, which will give the greatest rigidity (stiffness) for a given bar size with deformation along the bar axis (bending or axial). Pultrusion isn't really that well suited to producing sheets and is a bit limited for non-unidirectional fibre direction options.

Vacuum injection (VARTM, etc.) is more suited to somewhat lower fibre volumes (often 50-55%) and large sheet areas, with preference usually given to cloth and non-crimp fabric reinforcements, though small fitting-like components can also be infused economically.

The two manufacturing methods are sufficiently different that usually they are not considered alternatives for a given form of structure.

An exception might be beams of constant section such as those sometimes used in truck beds.

What are you making?

 

[carbongr]

thanks for the help.
i am producing UD carbon fibre bars.
According to your indications, pultrusion is best for my case, and this is what i'll do.

 

[spudpeeler]

If the part count is high pultrusion is the best way forward. If the part count is not in the hundreds I would consider a vacuum molding process or press molding with prepreg.

 

[bobbywvu]

If you are manufacturing UD fiber bars, use pultrusion.You can also make a hand pultrusion unit if you don't require continuous production. It is difficult to make rods using vaccum bagging and achieve better stiffness. Pultrusion yields better stiffness too.

 

[carbongr]

"hand pultrusion unit"

Can this be done?