Dissolvable mandrel

General Composites Discussions Equipment Talk
#1

Hi guys,

I’m in the middle of a research project that aims to create hollow composite parts for a ducting system (aircraft application).

The most interesting solutions at this point (from the research POV) are two-part clamshell molding + vacuum bag/pressure bladder, or the use of a dissolvable mandrel.

So far I’ve found one company (Stratasys) that is capable of producing these cores, which are 3D printed.

So, I ask you kind forum:

1 - Can anyone help me find more suppliers for this kind of materials?
2 - And could this material be modeled using a female clamshell mold rather than 3D printing?
3 - Does anyone know a dissolvable mandrel material that can withstand a curing cycle up to 350°F?

Best regards,
idiroft

#2

I believe Aquapour or Aquafoam or Aquacore (forgot the name, think it is the last) can do that. Mix powder with water, and you can pour it into a mould to make a core.

The core can be dissolved with water again.

#3

I used in the past when I worked in F1 a product called Aquacore.
There are two versions: a pourable one and a “compactable” moisted powder one.
It works, BUT…
It requires a LOT of heat to dry before the lay up and the external surface is similar to sand. (they sell a sealer to overcome that, but usual release agents don’t work well on it).
Anyway, it dissolves easily when flushed with water.

http://www.acmtucson.com/products/water-soluble-molds-and-tooling/raw-materials/aquacore.html

#4

Look I to pouring salt. I worked many a/c duct projects that used a female mold split in two. Aluminum toolin of course. Poured in molten salt. Layed up prepreg over the mandrel and then cooked in an autoclave. Salt was then hot pressure washed away.

Very easy and the salt tooling is very high quality. Aluminum tools are needed

#5

What kind of salt, and what temp does it melt?

#6

i think there is a specific type of salt that is best, but im not sure which… im retty sure table salt will work however.

BUT the cool part is that you dont melt the salt, it is dissolved away by water. some people soak it, but it is faster to remove it with a hot water pressure washing system. i always wondered personally if few cycles in a normal dishwasher would work, with no detergent of course.

-david

#7

Well we used a system where you melt the salt in a molten like state. Then you pour it into tooling and let it cool. It becomes hard as a rock. Then you can layup on it. Pressure wash it out.

#8

Eutectic salt mandrel … Wash out tooling… Eutectic wash out … will get you to a few companies that sell systems if u google them. We didn’t have too much issues with shrinkage once all the kinks were ironed out.

Issues were bubbles and voids in the pour causing tools to crack. We solved it with slower pours and using a paddle to work the salt into the tools.