Infusion of resin at 30 poise to dry fabric tow

[wongweiyew]

Dear all,

Does anyone know how of any technique of infusing a resin film with 30 poise viscosity (lowest in can go @ 250°F) to a highly compacted dry carbon tow of 24K strands? I've tried using vacuum bag at 28 in-Hg heat to 250°F and a dwell of 30 minutes but the core is dry. Will the use of positive pressure, say 85 psi helps? Are there any other technique available? Please advice.

Thanks!

 

[MikeHalloran]

How about starting with a loose tow and compacting after infusion?

( Since you're making scrap now, at least try using glass until you get the process working. )

... Wait a sec; you're starting with resin in film form, e.g. b-staged, or you're trying to infuse a film- shaped cavity? Either way sounds like a non- starter.



Mike Halloran
Pembroke Pines, FL, USA

 

[ewh]

Try forum327. Much good experience gathered there.

 

[MechanicalChef]

Positive pressure may help. If possible, evaluate your choice of resin. You're going to have a hell of a time trying to make a VARTM process work with a resin at 30 poise. The VARTM resins around here are usually at below 500 centi-poise.

 

[RPstress]

30 poise (3 pascal.seconds) should be doable for resin film infusion (RFI) under vacuum to achieve 55% or maybe 60% fibre volume fraction. If there's only enough resin for 60+% Vf or the final cured thickness being infused is > 15 thou (0.4 mm) per layer of resin then it'll get trickier. In theory external pressure (e.g., in an autoclave) should help. NB: glass should be less infusable than carbon. It may depend on how fast the resin's going off at that temperature.

Agree with ewh, the composites forum is a better bet to get infusion experts' attention.

 

[Compositepro]

Do you mean the core of the panel is dry or the core of the tow? 30 poise is not too high for RFI to work, but you don't say what the gel time is. Dry core is often due to poor vacuum which leaves air trapped in the fiber. Resin cannot infuse because the air cannot be displaced. You do also need to have sufficient resin to fill the empty spaces in the fiber and that depends on the bulk factor of the fiber. Higher compaction presure will reduce the bulk volume of the fiber, but only up to a point.